Search

The methods of Raman spectroscopy, scanning electron microscopy, atomic force microscopy, and X-ray fluorescence microanalysis are used to study the influence of tin on the shape and sizes of micro- and nano-structures arising on the surface of layered Si–Sn–Si films, as well as on the formation of Si nanocrystals in them during the tin-induced crystallization of amorphous silicon. In this work, the problems dealing with the experimental evaluation of the formation efficiency of Si nanocrystals in Si–Sn–Si films, the determination of the forms and scales of the film surface roughness, and the micro-distribution of impurities over the film surface and across the film thickness are tackled. The possibility of the formation of Si nanocrystals a few nanometers in size over most of the Si–Sn–Si film volume is experimentally confirmed. It is established for the first time that, during the production of such films using the thermal vacuum sputtering method, the thickness of a tin layer and its ratio to the thickness of silicon layers determine the shape and scale of the periodic surface relief structuring, which is important for the production of electronic devices. Quasi-spherical formations from 20 nm to 2–3 μm in diameter turned out to be the main element of the film surface relief structuring. The surface roughness induced by them can vary from a few nanometers to several tens of nanometers, depending on the layer deposition conditions. The shape of surface formations can change from cluster-like dendrites of the fractal type to convex ellipsoids and polygons. It is shown that the primary structuring occurs as the formation of a layer of hemispherical tin microdroplets already in the course of tin deposition. The secondary structuring occurs at the stage, when the second layer of silicon is deposited onto the layer of tin hemispheres. At this stage, a layer of the amorphous semiconductor is formed on the surface of the liquid metal, and this phenomenon is studied for the first time. The so-obtained amorphous silicon has a porous structure and consists of cluster-like dendrites of the fractal type about hundreds of nanometers in scale. The smallest dendrite elements also have a quasi-spherical shape 20–50 nm in diameter. Possible applications of the obtained results are discussed., Методи Раманiвської спектроскопiї, растрової електронної мiкроскопiї, атомно-силової мiкроскопiї i рентґено-флуоресцентного мiкроаналiзу застосованi з метою дослiдження впливу олова на форму i розмiри мiкро- та наноструктури поверхнi шаруватих плiвок Si–Sn–Si, а також на утворення в них нанокристалiв Si пiд час iндукованої оловом кристалiзацiї аморфного кремнiю. В данiй роботi вирiшувалися задачi експериментальної оцiнки ефективностi формування нанокристалiв Si в плiвках Si–Sn–Si, а також визначення форм i масштабiв шорсткостi поверхнi плiвок, мiкророзподiлу домiшок по їх площi i перерiзу. Експериментально пiдтверджено можливiсть формування нанокристалiв Si масштабу одиниць нанометрiв в бiльшiй частинi об’єму плiвок Si–Sn–Si. Вперше встановлено, що при виготовленнi таких плiвок методом термiчного вакуумного напилення товщина шару олова та її спiввiдношення з шарами кремнiю визначають форму i масштаб перiодичної структуризацiї рельєфу поверхнi, яка важлива для виготовлення реальних електронних приладiв. Головним елементом структурування рельєфу поверхнi плiвок виявилися квазисферичнi утворення дiаметром вiд 20 нм до 2–3 мкм. Зумовлена ними шорсткiсть поверхнi змiнюється в дiапазонi вiд одиниць до кiлькох десяткiв нанометрiв залежно вiд умов осадження шарiв. Форма поверхневих утворень змiнюється вiд гроно-подiбних дендритiв фрактального типу до опуклих елiпсоїдiв i багатокутникiв. Показано, що первинне структурування вiдбувається у виглядi утворення шару пiвсферичних мiкрокрапель олова вже у процесi його осадження. Вторинне структурування вiдбувається на етапi осадження другого шару кремнiю на шар олов’яних пiвсфер. На цьому етапi вiдбувається формування шару аморфного напiвпровiдника на поверхнi рiдинного металу, що дослiджувалось вперше. Отриманий таким чином аморфний кремнiй має порувату структуру, що складається з гроно-подiбних дендритiв фрактального типу масштабу сотень нанометрiв. Найменшi елементи дендритiв теж мають квазисферичну форму дiаметром 20–50 нм. Отриманi результати обговоренi з точки зору можливих застосувань.

The degradation of two amorphous silicon-based photovoltaic (PV) modules, namely, of single junction amorphous silicon (a-Si) and of micromorph tandem (a-Si/μ-Si), after 11 years of exposure in the south of Spain is analyzed. Their I-V curves were measured outdoors to study the changes of the electrical parameters in the course of three different periods: during the initial days of exposure, during the first year, and in the subsequent 10-year period. The translation of the curves to an identical set of operating conditions, which enables a meaningful comparison, was done by the dif ferent correction procedures described in the standard IEC60891:2021, including the procedure 3, which does not require the knowledge of module parameters, whose values are typically not available. The annual power degradation rates over the entire 11-year period are 1.12% for the a-Si module, which is 3.02% for the first year, and 0.98% for the a-Si/μ-Si, which is 2.29% for the initial year This work is supported by Ministero dell'Istruzione, dell'Università e della Ricerca (Italy) (grant PRIN2020-HOTSPHOT 2020LB9TBC and grant PRIN2017-HEROGRIDS 2017WA5ZT3_003); Università degli Studi di Salerno (FARB funds); Ministerio de Ciencia, Innovacion y Universidades (Spain) (grant RTI2018-095097-B-I0).

Demand for efficient window layer in thin film solar cells with high crystallinity is ever increasing that finds important application in multi-junction/tandem silicon solar cells. Doping of diborane (B2H6) in hydrogenated silicon films using plasma discharge decomposition of silane (SiH4) and (B2H6) gases were analyzed. The boron flow (FB) to silane ratio was varied from 0–0.30. Variation in film characteristics with B2H6 gas-phase ratio were analyzed, and concluded that doping boron induces crystallization in hydrogenated amorphous silicon (a-Si: H) film structure. The Raman and field emission scanning electron spectroscopy (FESEM) confirmed the boron induced crystallinity effect in silicon films at different diborane flow. The results showed that as boron content increases beyond certain ratio, silicon crystallization suppresses and the crystallite sizes were also reduced. From results, it was observed that crystallinity in FB = 0.05 is 79 % and decreases to 77 % when films are slightly higher doped (FB = 0.10) and further decreases when the films were heavily doped. These results validate that boron suppresses silicon crystallization due to local deformations caused by the impurities. Infra-red absorption studies and their analysis also confirm the crystallization in boron doped films with additional band appears at ~ 611 cm− 1. This band is named as boron induced crystallinity mode of vibrational spectra. The estimated hydrogen content (CH) decreases confirmed crystallinity in the silicon structure with boron doping. Further, the energy dispersive spectroscopy (EDX) indicates the presence of boron and other impurities in deposited silicon films. The effect of boron on crystallinity and crystallite size as well as the mechanism were presented in detailed.

Photoelectrochemical water splitting devices require semiconductor photoelectrode material fulfilling a number of primary requirements such as band gap, band edge alignment and corrosion resistance to electrolyte. Amorphous silicon carbide films, undoped and doped (P or B), were deposited on Si substrates by PECVD technology. The concentration of elements in the films was determined by RBS and ERD analytical method. Raman spectroscopy study of the SiC films were performed by using a Raman microscope and chemical compositions were analyzed by FTIR, before and after immersion of samples to aqueous pH 2.0 and pH 1.0 sulfuric acid electrolyte. Electrical properties of SiC films before and after immersion of samples to aqueous pH 2.0 and pH 1.0 sulfuric acid electrolyte were studied by measurement of the I–V characteristics on structure Al/SiC/Si/Al. Differences between Raman spectra, FTIR spectra and I–V characteristics before and after immersion to electrolyte are discussed.

A thin intrinsic hydrogenated amorphous silicon carbide ((i) a-SiCx:H) layer with a wide band gap attracts attention as an alternative passivation layer instead of intrinsic hydrogenated amorphous silicon ((i) a-Si:H) for heterojunction photovoltaic applications. The optical band gap of (i) a-SiCx:H can be widened up to 2.24eV. An increase in the optical band gap makes this layer appropriate as the window material by reducing the parasitic absorption. However, the deposition regime should be investigated to understand the incorporation of carbon. The influence of several deposition parameters such as precursor gasses flow rates and plasma power density on the (i) a-SiCx:H layers were investigated in optical, electrical, and elemental aspects. Relatively high interface trap densities were detected related to carbon piling up at the interface. An increase in the amount of C in the interface affected the passivation quality and fixed charge density of the layer. The ratio of secondary ion intensities measured by time of flight-secondary ion mass spectroscopy presents general hydrogen filling of possible dangling bonds and the bonding preferentiality between the silicon or carbon atoms. The passivation quality of the (i) a-SiCx:H layer partially enhanced by stack layer deposition of (i) a-Si:H/(i) a-SiCx:H resulting effective lifetime above 100 μs.

Global scenario of solar energy is increasing exponentially to mitigate environmental pollution and reduce the dependency on fossil fuels. In this sequence the research is continue to enhance the use of solar PV based panels for electricity generation. The companies across the globe are manufacturing several kinds of PV panels and these are utilized everywhere based on the generalized performance. Since these PV panels power drop with increase the temperature so it is now necessary to provide the choice for customers by emphasizing the temperature dependent local site performance. In this an analysis is conducted for a local site in Mathura where a 50kWp polycrystalline based project is installed. This analysis suggest that the PR for different technologies is 79.17%, 72.15%, 41.02%, 65.56%,56.45% and 97.27% respectively for mono crystalline, polycrystalline, amorphous silicon, Copper Indium Gallium Selenide, cadmium telluride and HIT. More over HIT -most suitable with fatigue life 6 years, mono crystalline -more suitable with fatigue life 5 years, poly crystalline – suitable with fatigue life 4 years, CIS – less suitable with fatigue life 3 years, CDTe-Lesser suitable with fatigue life 2 years and Amorphous- Least suitable with fatigue life 1 years.

The dopant-related issues are amongst the major performance bottleneck in crystalline silicon solar cells that can be alleviated via implementation of dopant-free layers. This work presents the implementation of tungsten oxide (WOx) and titanium oxide (TiOx) as hole- and electron-selective films for heterostructure solar cell design whereby n-type Si wafer has been passivated with ultrathin silicon oxide (SiO2) layer. Several designs have been investigated including passivated hydrogenated amorphous silicon (i-a-Si:H) and characterized by evaluating work function, electron affinity, interfacial charge, and layer thickness. The high work function of WOx induces significant upward band bending to permit holes transportation towards anode, whereas, low electron-affinity for TiOx reduces the barrier against electrons at the cathode. Smaller band offsets have been observed against minority carriers for devices that employ passivated i-a-Si:H film. However, incorporating SiO2 significantly improves the energy barrier height against minority carriers that leads to an enhancement in electric field along with reduction in recombination. The best-performance device with an optimum SiO2 thickness of 1 nm numerically validated V-oc of 751 mV, J(sc) 40.2 mA/cm(2), FF 79.7%, and rl of 24.06%. A comparative analysis with hole-selective vanadium oxide (V2Ox) demonstrated eta of 21.73% limited by the low work function of V2Ox. (C) 2021 Elsevier Ltd. All rights reserved.

Heterojunction c-Si and hydrogenated amorphous silicon (a-Si:H) devices with intrinsic a-Si:H thin layer, known as HIT solar cells, are promising alternatives to conventional c-Si solar cells for the possibility of higher open circuit voltage, low temperature processing and lower costs. We have studied the influence of the properties of p-a-Si:H layer and the work function of the front electrode material on the performance parameters of n-c-Si based HIT solar cells using numerical simulation. The findings are further analyzed using energy band diagrams and carrier concentration profiles at the heterointerface of a-Si:H/n-c-Si to reveal the underlying charge transport mechanisms.

V doktorski disertaciji smo se osredotočili na simulacije, načrtovanje in eksperimentalno demonstracijo fotonskih integriranih vezij (PIC) na osnovi silicija, ki vsebujejo in izkoriščajo izbrane nanofotonske strukture za izboljšanje zmoglivosti in funkcionalnosti integriranih fotonskih gradnikov. Posvetili smo se predvsem podvalovnodolžinskim nanostrukturam dielektričnih metamaterialov v vlogi obloge optičnih valovodov v PIC. Poleg standardne platforme silicija na izolatorju (SOI), ki vsebuje kristalni silicij, smo v raziskave vključili tudi hidrogenizirani amorfni silicij (a-Si:H) kot potencialni material za fotonsko integracijo. Demonstrirali smo testno a-Si:H vezje z vključenimi nanofotonskimi strukturami. V sklopu disertacije smo uporabili različne numerične modele, ki smo jih prilagodili za simulacije nanofotonskih struktur in gradnikov PIC. Razvili smo tudi merilni sistem za optično karakterizacijo PIC, ki omogoča stransko in navpično sklapljanje PIC-a z dvemi optičnimi vlakni. Dielektrične metamateriale smo raziskovali v vlogi obloge optičnih valovodov z namenom večanja gostote integracije PIC. Raziskali smo tudi vpliv lomnega količnika (različne materialne platforme za izdelavo PIC) na pojave metamaterialne obloge. Rezultati kvantitativne analize so pokazali, da je vpliv metamaterialne obloge na gostoto integracije lahko pozitiven le v platformah z visokim kontrastom lomnih količnikov (kot na primer Si ali InP membranska platforma). V nadaljevanju smo izvedli obširnejšo optimizacijo geometrije metamaterialne obloge za primer Si platforme z namenom zmanjšanja minimalno dopustne širine med jedri dveh optičnih valovodov, pri čemer smo omejili vrednost presluha na -30 dB pri dolžini 2 mm. Tako smo lahko eksplicitno kvantitativno ocenili povečano gostoto integracije gradnikov na PIC. Z vpeljavo metamaterialne obloge smo dosegli zmanjšanje minimalne dopustne reže med jedri dveh trakastih valovodov za 60 % v primerjavi s Si valovodi z običajno oblogo. Raziskali smo tudi valovnodolžinsko odvisnost in občutljivost na variacije dimenzij pri izdelavi optimiziranih struktur. Rezultati razkrivajo, da je potreben kompromis med največjo dosegljivo gostoto integracije in uporabnim valovnodolžinskim območjem. Optične lastnosti dielektričnih metamaterialov lahko koristno uporabimo tudi pri delitvi polarizacije v PIC. V disertaciji predlagamo koncept polarizacijskega razcepnika (PBS), ki izkorišča edinstvene lastnosti dielektričnih metamaterialnih oblog za dosego največjega dušenja (ER) in največje pasovne širine (BW). Kot izhodišče smo vzeli strukturo (PBS-1), ki je osnovana na smernem sklopniku z metamaterialno oblogo, ki smo ga združili z zavojem valovoda z metamaterialno oblogo na zunanji strani, v vlogi TE polarizatorja. Z namenom povečanja BW smo predlagani izboljšani koncept (PBS-2) - strukturo s kompaktnim dvojnim Mach-Zehnderjevim interferometrom v kombinaciji s TE polarizatorjem. Numerične simulacije so razkrile, da lahko s tako strukturo dosežemo izjemno visoko ER nad 35 dB in 263 nm široko BW z vstavitvenim slabljenjem (IL) 1 dB. Načrtani gradnik PBS-2 ima velikostni odtis 82 μm. Rezultati meritev izdelanega gradnika PBS-2 so razkrili, da je eksperimentalno doseženo ER > 30 dB v in BW vsaj 140 nm (omejeno območje nastavljivega laserja). Na področju a-Si:H materialov za fotonsko integracijo smo demonstrirali načrtovanje, izdelavo (v sodelovanju z zunanjimi partnerji) in karakterizacijo PIC s testnimi strukturami za sklopitev z optičnimi vlakni ter testnimi strukturami valovodov z metamaterialno oblogo. Izvedli smo analizo z vrstičnim elektronskim mikroskopom (SEM) za oceno kvalitete izdelave struktur z minimalnimi dimenzijami 60 nm. Rezultati analize so pokazali, da so bile strukture, kljub majhnim dimanzijam, po optimizaciji procesa z uporabo elektronskega snopa (e-beam) izdelane kvalitetno. Izmerjena vršna vrednost sklopne učinkovitosti sklopnika z uklonsko mrežico (s strukturami manjšimi od valovne dolžine svetlobe minimalne dimenzije 78 nm) je bila -7.25 dB. Rezultati meritev testnih struktur valovodov z metamaterialno oblogo eksperimentalno potrjujejo teoretično predvideno znižanje presluha v takih strukturah a-Si:H. V primeru metamaterialne obloge z dvemi rebri smo dosegli znižanje presluha za 15 dB v primerjavi z običajnimi valovodi. Na osnovi prikazanih rezultatov v doktorski disertaciji upamo in verjamemo, da naši rezultati prispevajo nova znanja k področju integrirane fotonike. Prikazane lastnosti dielektričnih metamaterialov se lahko koristno uporabijo, ko je zahtevana velika gostota integriracije optičnih valovodov. Verjamemo tudi, da je lahko demonstriran koncept in zmogljivost polarizacijskega razcepnika, ki izkorišča metamaterialno oblogo, uporabljen v aplikacijah, ki zahtevajo učinkovito deljenje polarizacije. Demonstracija uspešne sklopitve a-Si:H PIC z optičnimi vlakni predstavlja prvi korak k nadaljnim raziskavam a-Si:H materialov za PIC, ki jih načrtujemo v prihodnosti. Prikazani rezultati predstavljajo izhodiščno točko za raziskave vpliva parametrov depozicije a-Si:H plasti za kontrolo nad kristalno zgradbo in hidrogeniziranostjo a-Si:H plasti in njihovega vpliva na zmogljivostne parameter gradnikov PIC, kot so kvaliteta izdelave nanostruktur, valovodne izgube in nelinearne lastnosti. In this thesis, we focus on simulations, design and experimental demonstration of silicon-based photonic integrated circuits (PICs) utilizing nanophotonic structures to increase the performance and alter the functionality of integrated devices. Furthermore, we study hydrogenated amorphous silicon (a-Si:H) as a potential material for PICs and demonstrate a test a-Si:H PIC utilizing nanophotonic structures. Different numerical models were utilized and adapted to simulate specific nanophotonic structures and PIC components in the scope of this thesis. An experimental measurement set-up for optical characterization of PICs in horizontal and vertical fiber coupling configuration was developed as well. In this thesis all-dielectric metamaterials are the main nanophotonic structures under investigation. We study them in the role of the cladding of optical waveguides (WGs) to increase the integration density of PICs. The role of the refractive index (material platform) on the effects of metamaterial cladding is studied. The results of a quantitative analysis show that only material platforms with a high refractive index contrast (such as existing Si or membrane InP platform) can noticeably benefit from optimized metamaterial cladding in terms of integration density. Furthermore, we perform a comprehensive optimization of the geometry of metamaterial cladding in Si platform to achieve the lowest possible gap width between cores of two adjacent WGs, while keeping the cross-talk bellow the targeted limit of -30 dB at the length of 2 mm. By doing this we can explicitly show how much the integration density of a PIC can be increased. We demonstrate that a metamaterial cladding can, in best case, reduce the gap width by 60 % compared to Si WGs with normal cladding in case of core width Wcore = 450 nm. The wavelength dependence and sensitivity to fabrication variability of optimized structures are also studied, revealing a trade-off between the highest possible integration density and a usable wavelength range. The demonstrated properties of all-dielectric metamaterial cladding structures can also be utilized in polarization splitting. We propose a concept of integrated silicon-based polarization beam splitter (PBS) exploiting unique properties of all dielectric metamaterial cladding to achieve a high extinction ratio (ER) and wide bandwidth (BW) polarization splitting characteristics. We start from a structure (PBS-1) based on a directional coupler with metamaterial cladding combined with a bent waveguide with metamaterial cladding at the outer side in the role of a TE polarizer at the Thru port of the device. To increase BW we propose the improved concept (PBS-2) - a metamaterial compact dual Mach-Zehnder Interferometer structure in combination with the TE polarizer. Numerical simulations reveal that an exceptionally high ER over 35 dB can be achieved in a BW of 263 nm with insertion loss (IL) below 1 dB in case of PBS-2. The designed device has a footprint of 82 μm. We also fabricate the device via a commercially available fabrication service. Measurement results reveal that an ER > 30 dB is achievable in a BW of at least 140 nm (limited by the laser tuning range). In the field of a-Si:H materials for photonic integration we demonstrate the design, fabrication (in conjunction with external partners) and characterization of a PIC with test structures for light in/out coupling as well as some test structures of WGs with all-dielectric metamaterial cladding. A scanning electron microscopy (SEM) analysis was carried out to evaluate the fabrication of structures with the minimal feature size of 60 nm, revealing good results in terms of subwavelength structure development. The measured peak coupling efficiency of a single etch-step subwavelength grating coupler (exhibiting a minimal feature size of 78 nm) was -7.25 dB. The measurements of test structures of WGs with all-dielectric metamaterial cladding experimentally confirm the predicted decrease in cross-talk in such structures. Namely, a reduction in cross-talk by 15 dB was achieved for a metamaterial cladding test structure with two ribs. We hope and believe that the results presented in this thesis can contribute to the field of integrated photonics. The demonstrated qualities of the all-dielectric metamaterial cladding can be of use in case of applications requiring densely integrated WGs. Furthermore, we believe that the demonstrated design and performance of the PBS utilizing a metamaterial cladding is to be utilized in PICs for applications where high performance polarization splitting is required. The demonstration of successful light in/out coupling to the a-Si:H PIC represents the first step towards our future investigations a-Si:H materials in PICs. It presents a starting point for future study of the a-Si:H layer deposition parameters resulting in different levels of crystallinity and hydrogenization on various PIC performance metrics such as quality of fabrication, WG propagation loss and non-linearity.

This study identifies unstable and soluble layers in commercial photovoltaic modules during 1.5 year long-term leaching. Our experiments cover modules from all major photovoltaic technologies containing solar cells from crystalline silicon (c-Si), amorphous silicon (a-Si), cadmium telluride (CdTe), and copper indium gallium diselenide (CIGS). These technologies cover more than 99.9% of the world market. We cut out module pieces of 5 &times, 5 cm2 in size from these modules and leached them in water-based solutions with pH 4, pH 7, and pH 11, in order to simulate different environmental conditions. Unstable layers open penetration paths for water-based solutions, finally, the leaching results in delamination. In CdTe containing module pieces, the CdTe itself and the back contact are unstable and highly soluble. In CIGS containing module pieces, all of the module layers are more or less soluble. In the case of c-Si module pieces, the cells&rsquo, aluminum back contact is unstable. Module pieces from a-Si technology also show a soluble back contact. Long-term leaching leads to delamination in all kinds of module pieces, delamination depends strongly on the pH value of the solutions. For low pH-values, the time dependent leaching is well described by an exponential saturation behavior and a leaching time constant. The time constant depends on the pH, as well as on accelerating conditions such as increased temperature and/or agitation. Our long-term experiments clearly demonstrate that it is possible to leach out all, or at least a large amount, of the (toxic) elements from the photovoltaic modules. It is therefore not sufficient to carry out experiments just over 24 h and to conclude on the stability and environmental impact of photovoltaic modules.

The influence of silicon nanowire (SiNWs) geometry on the efficiency of radial p-i-n junction solar cell is studied using experimental measurements. Solar cells based on vertically aligned structures with the SiNWs less than 10 µm in height are practically on par with the planar element in terms of the open-circuit voltage, exceeding it in terms of short-circuit current density by up to 1.5 times (3.9–4.9 mA/cm2). The increase in the short-circuit current density is associated with the broadening of the quantum efficiency (EQE) spectrum. There is a significant broadening of the EQE boundary to the short-wavelength region with a decrease in the diameter of the SiNWs (from 1.8 to 0.8 µm). A decrease in the open-circuit voltage and a decrease in the absolute value of EQE are observed for structures with SiNWs more than 10 µm in height., В работе исследуется влияние геометрии кремниевых нановолокон (КН) на производительность солнечных элементов на основе радиальных p-i-n a-Si:H структур, осажденных на КН. Солнечные элементы на основе вертикально-ориентированных структур с высотой КН менее 10 мкм по значениям напряжения холостого хода практически не уступают планарному элементу, а по значениям плотности тока короткого замыкания превосходят его до 1.5 раз (3.9–4.9 мА/см2). Увеличение значения тока короткого замыкания связано с расширением спектра квантовой эффективности, причем с уменьшением диаметра кремниевых нановолокон (с 1.8 до 0.8 мкм) наблюдается существенное расширение границы спектра квантовой эффективност в коротковолновую область. Для структур c высотой кремниевых нановолокон более 10 мкм отмечается снижение значения напряжения холостого хода и уменьшение абсолютного значения EQE.

Variable resolution fluctuation electron microscopy experiments were performed on self-ion implanted amorphous silicon and amorphous germanium to analyze the medium-range order. The results highlight that the commonly used pair-persistence analysis is influenced by the experimental conditions. Precisely, the structural correlation length Λ, a metric for the medium-range order length scale in the material, obtained from this particular evaluation varies depending on whether energy filtering is used to acquire the data. In addition, Λ depends on the sample thickness. Both observations can be explained by the fact that the pair-persistence analysis utilizes the experimentally susceptible absolute value of the normalized variance obtained from fluctuation electron microscopy data. Instead, plotting the normalized variance peak magnitude over the electron beam size offers more robust results. This evaluation yields medium-range order with an extent of approximately (1.50 ± 0.50) nm for the analyzed amorphous germanium and around (1.10 ± 0.20) nm for amorphous silicon.

The structural investigation of the a-Si:H material, deposited at different pressures by PECVD process, has been carried out to analyze the signatures of diffused intermediate sort of crystalline phases within the amorphous silicon matrix. Raman characterization along with the Photoluminescence (PL) and spectroscopic ellipsometry studies were carried out to understand the microstructuree of these films. From Raman analysis the material was found to have indistinguishable crystalline phase, which can also be named as “intermediate amorphous phase” (a phase defined between amorphous and ultra nano-crystalline silicon) with crystalline volume fractions as 56 % and 62 % for 0.23 Torr and 0.53 Torr respectively. Here the contribution of ultra nano-crystallites results in higher crystalline fraction, which is not visibly revealed from the Raman spectra due to its sub nano-crystallite characteristics. For the film deposited at 0.53 Torr stable photo-conductance in conjunction with high photo-response under 10 hour light soaking has been observed, which is as expected due to high crystalline volume fraction. The presence of these phases might be the possible reason for the distinct device characteristics though having nearly the similar electrical properties (photo-response ~10 4 ). These studies will help to make improvement in the individual layer properties, other than the interface effect, in the fabrication of efficient p-i-n solar cells. Copyright © 2016 VBRI Press

The photovoltaic device's economic and environmental merits have made it the most suitable clean energy alternative to help developing countries achieve the SDG-7. However, the low efficiency of the device, which is undergoing massive study across the globe, there is another omnipresent factor, such as surface soiling that has a deleterious effect on a solar cell's performance, which is influenced by wind speed/direction, humidity and temperature. This study investigates the impact of dust on four PV types (Monocrystalline Silicon, Polycrystalline Silicon, Cadmium Telluride and amorphous Silicon) in a city with two large commissioned and one massive solar farm under construction considering wind, humidity, rain, temperature and dust particles under extreme conditions. Low iron glass coupons were also exposed in seasonal, monthly, and annual categories to determine optical losses, soiling rates, and deposition mass. Accumulated dust particles on the surface of the coupon were subjected to SEM/EDX imaging to identify the deposited minerals' morphology. The findings reveal a massive performance decline due to soiling on all exposed modules with a most significant ISC decrease recorded about 73% on a-Si and least about 65% of the Si modules in one year without cleaning and a total of seventeen months exposure. The outcome shows significant losses recorded, where a yield loss of 78.3% and efficiencies decline of 78% for amorphous Si, 77% and 77% for cadmium telluride, 70% and 71% for polycrystalline and 68.6% and 71% for the monocrystalline Si module. A wide variation of performance losses was recorded between months and seasons in 2021, and the dry season presented the most alarming rates. The optical loss results validated the above output performance losses with a similar trend. The particle characterisation reveals that mineral particles > PM10 size with opaque and translucent morphology were the main constituent of dust formation on the examined coupons. It is recommended to study various mitigation techniques and use the correct one in an optimal cycle, which is cost-effective, which could restore and maintain the installation's optimal efficiency.

This paper reports the successful fabrication of softening polymer (SP)-based devices with inter-layer coatings for neural interface applications. SPs are flexible biocompatible polymers that soften upon implantation into the body, thus capable of reducing mechanical stress on the surrounding tissue and increasing the conformability of the implant. The softening process relies on water uptake into the polymer that can affect its electrical insulation capabilities. Employing an amorphous silicon carbide (a-SiC) thin film inter-layer between the metal traces and the SP is expected to provide a reliable water-barrier while allowing the SP plasticization once the device is implanted. We report the electrochemical properties and leakage current characteristics of various structures with a-SiC and polyimide inter-layer coatings under simulated physiological conditions. The fabricated structures demonstrated appropriate electrical properties and were found to be reliable up to a 2.5 mm radius of curvature when bending in compression.

Reducing the parasitic absorption of intrinsic hydrogenated amorphous silicon [a-Si:H(i)] films is crucial for enhancing the short-circuit current density (Jsc) of silicon heterojunction (SHJ) solar cells. Herein, a-Si:H(i) films were replaced by intrinsic hydrogenated amorphous silicon oxide [a-SiOx:H(i)] films with wider band gap at the front of rear-emitter SHJ solar cells and the microstructure of a-SiOx:H(i) films was modified with the flow ratio of carbon dioxide to silane. A-SiOx:H(i) films showed lower absorption coefficients at short wavelengths and led to a 0.13 mA/cm2 absolute increase of Jsc. Additionally, higher open-circuit voltages (Voc) were achieved thanks to the better interface passivation and the fill factors (FF) almost kept constant due to avoiding the impediment of hole transport. However, the higher oxygen content in a-SiOx:H(i) films associated with the worse electrical performance hence carbon dioxide-to-silane flow ratio should be adjusted at a low value. Finally, a conversion efficiency (Eff) gain of 0.12%abs was obtained for the optimized SHJ solar cells as a result of the improvements of both Voc and Jsc. More importantly, a-SiOx:H(i) layer exhibited better damp-heat stability than a-Si:H(i) layer in sodium environment. This work clearly interpreted the functions of oxygen atoms in a-SiOx:H(i) films and offered a valid approach to reducing the parasitic absorption losses of SHJ solar cells.

Solar cells based on thin crystalline silicon (c-Si) substrates have the potential to provide relevant efficiencies with less material. In this article, we report on the fabrication of thin solar cells starting from a 20 μ m-thick c-Si wafer. Special attention is paid to optical performance of the rear surface where we need very high internal reflection and light scattering to improve light trapping properties of the device. In this sense, we introduce a texturization of the rear surface, which is excellently passivated by aluminium oxide films. In addition, for the rear contacts we use metal-covered wide-bandgap materials to improve back reflectance with a Vanadium Oxide/c-Si heterojunction for the emitter regions while the base contacts are defined by laser processing phosphorus doped amorphous silicon carbide films. Best solar cell has a reasonable efficiency of 8.7% and, more importantly, external quantum efficiency measurements demonstrate a better performance for photons with λ > 900 nm than in the case of a flat rear surface.

Ion irradiation induced nucleation and growth of nanoparticles in amorphous SiC at elevated temperatures are investigated in this study. Both as-deposited amorphous and Kr ion irradiation-amorphized SiC films are used for the investigation. Similar behavior of particle precipitation in the two types of the films is observed. It is found that the threshold temperature for nucleation is between 550 and 700 K, which is considerably higher than the critical temperature for full amorphization in SiC irradiated with Kr ions. There is a temperature regime up to at least 900 K, where the nucleation and growth rates are only weakly dependent of the irradiation temperature. This temperature regime is potentially useful to tailor the size and density of nanocrystalline SiC precipitates by optimizing the ion irradiation conditions.

It is generally known that a layer of amorphous silicon oxide (SiO2) naturally exists on the surface of silicon, resulting in the growth of gallium oxide (Ga2O3) that is no longer affected by substrate crystallinity during sputtering. This work highlights the formation energy between the native amorphous nano-oxide film formed on the Si substrate and monoclinic β-Ga2O3 dominating the preferred orientation prepared for deep ultraviolet photodetectors. The latter were deposited on p-type silicon (p-Si) with (111) orientation using radio frequency sputtering at 600 °C and post rapid thermal annealing (RTA). The X-ray diffraction (XRD) results indicate both as-deposited and postannealing films with the (400) preferred orientation for a layer thickness of 100 nm. However, slight random orientation with the amorphous structure is mixed in the preferred one for the as-deposited film with a thickness of 200 nm and reduced after being annealed at 800 °C, which is observed by XRD and transmission electron microscopy. Meanwhile, thermal-induced massive twin boundaries (TBs) and stacking faults (SFs) were generated when annealed at 1000 °C, owing to the relaxation of lattice strain by the coherent interface. The interfacial bonding energy per unit area (E i) between β-Ga2O3 films with various facets ((001), (010), (100), and (201)) and amorphous SiO2 was calculated using density functional theory. The E i of β-Ga2O3 (100)/SiO2 reveals the highest value (0.289 eV/A2), which is consistent with the (100) preferred orientation of deposited films. The (100) preferred orientation is the driving force for TBs and SFs. The discrimination of responsivities and the photo/dark current contrast ratio (I ph/I dark) are inversely proportional to the amorphous structure, grain boundaries, TBs, and SFs. Therefore, optimum metal-semiconductor-metal photodetector performance is achieved for RTA-treated samples at 800 °C with an I ph/I dark of 3.91 × 102 and a responsivity of 0.702 A/W (λpeak = 230 nm) at 5 V bias for a 200 nm thin film.

The effect of plasma excitation frequency on the performance of intrinsic hydrogenated amorphous silicon (a-Si:H) films and heterojunction solar cells by radio-frequency (RF, 13.56 MHZ) and very-high-frequency (VHF, 40 MHZ) plasma-enhanced chemical vapor deposition (PECVD) have been investigated. The thickness and microstructure of intrinsic a-Si:H films were measured by spectroscopic ellipsometry and Fourier transform infrared spectroscopy (FTIR). The a-Si:H/c-Si interface passivation quality were determined by minority carrier lifetime and transmission electron microscopy (TEM). The current–voltage (I–V) performance of the HJT solar cells were also evaluated. The results reveal that a-Si:H films developed by RF-PECVD with a large area of parallel-plate reactors (> 1 m2) exhibit better thickness uniformity, lower microstructure factor, and higher minority carrier lifetimes. Hence HJT solar cells have achieved efficiency of 24.9%, compared with cell efficiency of 24.6% with intrinsic a-Si:H films developed by VHF-PECVD.

We investigate the inkjet printing of liquid silicon ink to form in situ doped and structured passivating contacts. The ink consists of neopentasilane oligomers in solvents and decomposes into amorphous silicon with a short anneal. By printing boron- and phosphorus-doped ink on silicon oxide, polycrystalline silicon on oxide (POLO) junctions for both p-type and n-type polarities (POLO²) are formed and the saturation current densities as low as 5 fA/cm2 are achieved for n+-POLO junctions. We perform a structured printing in interdigitated back contact (IBC) geometry achieving emitter and base fingers with an average finger height of up to 103 nm. The application of inkjet printing allows for a simplification of POLO and POLO2 solar cell processing. In particular, for POLO2-IBC cells, a lean process flow is facilitated.

This paper describes a study on a novel X-ray detector with photoinduced discharge (PID) readout devices. Especially, we demonstrated optical scanning X-ray imaging devices based on intrinsic hydrogenated amorphous silicon (i-a-Si:H) PID readout layer, on which a pixelated metal layer, molybdenum, is formed as a charge accumulation layer of $200~\mu \text{m}$ pitch for clearly defining the pixel in the lateral and longitudinal directions. We decided to use i-a-Si:H as a readout layer instead of amorphous selenium(a-Se) layer because the material of a-Se does not withstand standard wet fabrication processes like lift-off wet process. An X-ray absorption layer of $500~\mu \text{m}$ thick a-Se is formed by a thermal evaporation process. To optically switch on the i-a-Si:H PID readout layer, we use a narrow line-beam with a beam width of $50~\mu \text{m}$ consisting of a blue LED array, optical films, and GRIN lens array. The pixelated PID readout X-ray detector is $512\times512$ image resolutions with a $200~\mu \text{m}$ pitch, and the overall active dimension is 10.24 cm $\times10.24$ cm. The sensitivity of the pixelated PID readout X-ray detector is 302 pC/cm $^{2}\cdot $ mR at Normal X-ray Tube conditions (IEC66220-1). According to MTF measurement results, the value of MTF0.1(10%) is measured at near 2.5 1/mm in the column direction scanning while the value is measured at 1.9-2.5 1/mm in the row direction scanning.

With the advantages of lower capacitance, faster operation and smaller size, the amorphous silicon antifuse is very promising for high-speed and high-density FPGA. However, the leakage current of the conventional amorphous silicon antifuse in the off-state is high, which decreases its performance and reliability. Although the leakage current of the SiNX or SiOX antifuse is small, the proper thickness of the dielectric layer is not easily controlled by PECVD processes. In addition, the highly undesirable switch-off behavior is common to almost all metal-to-metal antifuse structures. Focusing on the study of amorphous silicon multilayer dielectric structures, a novel antifuse with the structure of Al/α-Si:H,N/α-Si:H/Al was proposed, which was manufactured by nitrogen plasma treatment for an α-Si:H film surface. Through surface plasma treatment, the hydrogen content of the dielectric layer is stable, the film surface is smoother, the leakage current is reduced, the switch-off behavior is eliminated, the programming voltage is more concentrated and the on-state resistance distribution is more compact. The results demonstrated that surface plasma treatment with proper time for the dielectric layer could significantly improve the performance and reliability of the Al/α-Si:H,N/α-Si:H/Al antifuse. Furthermore, the fabrication process of the α-Si:H,N/α-Si:H structure has excellent compatibility, controllability and simplicity.

Femtosecond laser-modified amorphous silicon (a-Si) films with optical and electrical anisotropy have perspective polarization-sensitive applications in optics, photovoltaics, and sensors. We demonstrate the formation of one-dimensional femtosecond laser-induced periodic surface structures (LIPSS) on the surface of phosphorus- (n-a-Si) and boron-doped (p-a-Si) amorphous silicon films. The LIPSS are orthogonal to the laser polarization, and their period decreases from 1.1 ± 0.1 µm to 0.84 ± 0.07 µm for p-a-Si and from 1.06 ± 0.03 to 0.98 ± 0.01 for n-a-Si when the number of laser pulses per unit area increases from 30 to 120. Raman spectra analysis indicates nonuniform nanocrystallization of the irradiated films, with the nanocrystalline Si phase volume fraction decreasing with depth from ~80 to ~40% for p-a-Si and from ~20 to ~10% for n-a-Si. LIPSS’ depolarizing effect, excessive ablation of the film between LIPSS ridges, as well as anisotropic crystalline phase distribution within the film lead to the emergence of conductivity anisotropy of up to 1 order for irradiated films. Current–voltage characteristic nonlinearity observed for modified p-a-Si samples may be associated with the presence of both the crystalline and amorphous phases, resulting in the formation of potential barriers for the in-plane carrier transport and Schottky barriers at the electric contacts.

This work investigates how knock-on displacements influence fluctuation electron microscopy (FEM) experiments. FEM experiments were conducted on amorphous silicon, formed by self-ion implantation, in a transmission electron microscope at 300 kV and 60 kV at various electron doses, two different binnings and with two different cameras, a CCD and a CMOS one. Furthermore, energy filtering has been utilized in one case. Energy filtering greatly enhances the FEM data by removing the inelastic background intensity, leading to an improved speckle contrast. The CMOS camera yields a slightly larger normalized variance than the CCD at an identical electron dose and appears more prone to noise at low electron counts. Beam-induced atomic displacements affect the 300 kV FEM data, leading to a continuous suppression of the normalized variance with increasing electron dose. Such displacements are considerably reduced for 60 kV experiments since the primary electron's maximum energy transfer to an atom is less than the displacement threshold energy of amorphous silicon. The results show that the variance suppression due to knock-on displacements can be controlled in two ways: Either by minimizing the electron dose to the sample or by conducting the experiment at a lower acceleration voltage.

Poly-Si films were fabricated through crystallization of silicon oxide (SiOx, 0 ≤ x

Silicon-rich silicon nitride thin films are prepared on P-type monocrystalline silicon wafer (100) and glass substrate by plasma chemical vapor deposition with reaction gas sources SiH4 and NH3. The deposited samples are thermally annealed from 600°C to 1000°C in an atmosphere furnace filled with high purity nitrogen. The annealing time is 60 minutes. Fourier transform infrared spectroscopy (FTIR) is carried out to investigate the bonding configurations in the films. The results show that the Si-H bond and N-H bond decrease with the increase of annealing temperature, and completely disappear at the annealing temperature of 900°C. But the Si-N bond is enhanced with the increase of annealing temperature, and the blue shift occurs, then Si content in the film increases. The Raman Spectra show that the amorphous Si Raman peak appears at 480 cm-1 in the film at 700°C. The Raman spectra of the films annealed at 1000 °C is fitted with two peaks, and a peak at 497 cm -1 is found, which indicated that the Si phase in the films changed from amorphous to crystalline with the increase of annealing temperature. The experiment also analyses the luminescence properties of the samples through PL spectrum, and it is found that there are five luminescence peaks in each sample under different annealing temperature. Based on the analysis of Raman spectrum and FTIR spectrum, the PL peak of amorphous silicon quantum dots appears at the wavelength range of 525-555nm, and the other four PL peaks are all from the defect state luminescence in the thin films, and the amorphous silicon quantum dot size is calculated according to the formula.

Nickel-metal hydride (Ni-MH) batteries were widely used due to their various advantages, but its further application and development have been seriously hindered by the low electrochemical discharge capacity of conventional hydrogen storage alloy electrode. The hydrogenated amorphous silicon (a-Si:H) thin film electrode for Ni-MH battery has been proven to have a dramatic electrochemical capacity. We prepared a-Si:H thin films by a two-step process of rf-sputtering followed by hydrogenation, and investigated the effect of hydrogenation on the structure and electrochemical properties of which as an anode. The maximum discharge capacity of a-Si:H thin film electrode after hydrogenation increases from initial 180 mAh·g−1to 1827 mAh·g−1, which is over tenfold that of as-deposited hydrogen-less a-Si thin film electrode. Then, the preliminary relationships between hydrogen content and electrochemical performance of a-Si:H thin film electrode were analyzed, and several negative factors of electrochemical performance for a-Si:H thin film electrode were proposed.

In this paper, we propose the design and fabrication of a novel heterojunction semiconductor–insulator–semiconductor (SIS) front surface and interdigitated back-contact (IBC) solar cell. We approximate the performance parameters and loss analysis of the proposed solar cell using MATLAB software programming. Many studies have reported the experimental analysis of amorphous silicon (a-Si) IBC solar cells. A number of silicon heterojunction solar cell designs with promising efficiency have been reported in the past few decades. In this study, a long-lifetime (~ 2 ms) n-Si substrate was considered so that a sufficient number of photogenerated carriers could reach the interdigitated layer and be absorbed. The availability of carriers at the interdigitated back surface was further enhanced by considering a high-low junction created by a ZnO n+ layer at the front surface. A very thin layer of thermally deposited insulator SiO2 was considered between the ZnO and n-Si. This layer reduces the detrimental effects of interface defects. This is the first study in which we have theoretically investigated an IBC solar cell using metal oxide semiconductor layer deposition, thereby avoiding the expensive and complicated doping and diffusion process. In general, a high-concentration n+ layer is doped to create a high-low junction at the front to accelerate the transport of carriers to the back junctions. We propose a cost-effective method using thermal deposition of a SiO2 layer followed by sol–gel ZnO layer deposition, which serves the same purpose as an n+ layer by introducing an SIS junction potential at the front. The interdigitated back surface was designed with sequential n+ a-Si and p+ a-Si vertical junctions.

Kazuhisa Sato and Hirotaro Mori, Athermal Solid Phase Reaction in Pt/SiOx Thin Films Induced by Electron Irradiation, ACS Omega, 2021, 6 (33), 21837-21841., Microelectronics based on Si requires metal silicide contacts. The ability to form platinum silicide (Pt₂Si) by electronic excitation instead of thermal processes would benefit the field. We studied the effects of electron irradiation on Pt₂Si formation in composite films-composed of Pt and amorphous silicon oxides (a-SiOx)-by transmission electron microscopy and electron diffraction. Pt₂Si formed in Pt/a-SiOx bilayer and a-SiOx/Pt/a-SiOx sandwiched films by 75 keV electron irradiation, at 298 and 90 K. The reaction is attributable to dissociation of SiOx triggered by electronic excitation. In a-SiOx/Pt/a-SiOx sandwiched films, reflections of pure Pt were not present after irradiation, i.e., Pt was completely consumed in the reaction to form Pt₂Si at 298 K. However, in Pt/a-SiOx bilayer films, unreacted Pt remained under the same irradiation conditions. Thus, it can be said that the extent of the interfacial area is the predominant factor in Pt₂Si formation. The morphology of Pt islands extensively changed during Pt₂Si formation even at 90 K. Coalescence and growth of metallic particles (Pt and Pt-Si) are not due to thermal effects during electron irradiation but to athermal processes accompanied by silicide formation. To maintain the reaction interface between metallic particles and the dissociation product (i.e., Si atoms) by electronic excitation, a considerable concomitant morphology change occurs. Elemental analysis indicates that the decrease in Si concentration near Pt is faster than the decrease in O concentration, suggesting formation of a Si depletion zone in the amorphous silicon oxide matrix associated with formation of Pt₂Si.

In this article, silicon wafers were thermal treated in air at temperatures from 800 to 1200 °C. The annealed samples were investigated using X-ray diffraction, FTIR and optical reflection spectroscopy. Unique result obtained includes that, that Kubelk-Munk curves could be utilized to estimate the ratio of oxidized silicon atoms. In addition, we found that these curves could provide information on the degree to which the nanoparticle formation affects both the reflection spectra and the energy gap of the Si/SiO2 composites. On the other hand, it has been found that, the intensity of the silicon peak in XRD spectra is proportional to the relative absorption coefficient of amorphous silicon oxide.

We report a dual gate (DG), low-temperature polysilicon (LTPS) thin-film transistor (TFT) using blue laser annealing (BLA) of amorphous silicon. The DG TFTs with variable bottom gate lengths (LBG) from 2 to 8 $\mu \text {m}$ and a fixed top gate length (LTG) of 6 $\mu \text{m}$ are investigated. The drain currents of the DG LTPS TFT with LBG > LTG by 2 $\mu \text{m}$ under DG sweep (DS) are ~4.3 times those of the single gate TFT. The high carrier concentrations (~1019 cm−3) at both interfaces (top gate insulator (GI)/poly-Si and poly-Si/bottom GI) under DS is confirmed by technology computer-aided design (TCAD) simulation, which might lead to high drain currents. The poly-Si layer exhibits no grain boundary protrusion from the transmission electron microscopy (TEM) cross-sectional micrograph and thus induces a strong bulk accumulation effect under DS. The fabricated DG TFT-based ring oscillator (RO) and shift register (SR) exhibit an excellent oscillation frequency of 15.8 MHz, fast-rising and falling time of 370 and 366 ns at a driving voltage of −10 V, respectively.

A new process to crystallize amorphous silicon without melting and the generation of excessive heating of nearby components is presented. We propose the addition of a molybdenum layer to improve the quality of the laser-induced crystallization over that achieved by direct irradiation of silicon alone. The advantages are that it allows the control of crystallite size by varying the applied fluence of a near-infrared femtosecond laser. It offers two fluence regimes for nanocrystallization and polycrystallization with small and large crystallite sizes, respectively. The high repetition rate of the compact femtosecond laser source enables high-quality crystallization over large areas. In this proposed method, a multilayer structure is irradiated with a single femtosecond laser pulse. The multilayer structure includes a substrate, a target amorphous Si layer coated with an additional molybdenum thin film. The Si layer is crystallized by irradiating the Mo layer at different fluence regimes. The transfer of energy from the irradiated Mo layer to the Si film causes the crystallization of amorphous Si at low temperatures (∼700 K). Numerical simulations were carried out to estimate the electron and lattice temperatures for different fluence regimes using a two-temperature model. The roles of direct phonon transport and inelastic electron scattering at the Mo-Si interface were considered in the transfer of energy from the Mo to the Si film. The simulations confirm the experimental evidence that amorphous Si was crystallized in an all-solid-state process at temperatures lower than the melting point of Si, which is consistent with the results from transmission electron microscopy (TEM) and Raman. The formation of crystallized Si with controlled crystallite size after laser treatment can lead to longer mean free paths for carriers and increased electrical conductivity.

In this work, we report on the study of the electrical and optical properties of amorphous silicon carbide (a-SiC)-based Schottky diodes for optoelectronic applications. A significant decrease of reflectivity and an enhancement of the passivating properties of more than 97% were reached after a-SiC layer deposition on silicon substrate. The deposited a-SiC film exhibits a dielectric constant of 2.143. Temperature effect on Schottky diode performances was carried out through the analysis of the current–voltage (I–V) characteristics at temperature range of 298–573 K. The ideality factor at room temperature was found to be 1.651, and it was improved to 1.132 when temperature was increased to 573 K. The calculated barrier height of the diode at room temperature was c 0.812 eV and it increased with temperature to reach 1.640 at 573 K. The change in the barrier height was attributed to the effective leakage current at high temperature. Shunt resistance Rsh remained at around 85 KΩ along this range with a slight decrease at high temperature. Series resistance Rs was sharply decreased from 520 Ω at room temperature to 45 Ω at 573 K. Thanks to the optical and electrical characterization performed, we have demonstrated the possibility of using such non hydrogenated amorphous SiC layers to improve the properties of based silicon Schottky diodes.

Metal-ceramic nanocomposites exhibit exceptional mechanical properties with a combination of high strength, toughness, and hardness that are not achievable in monolithic metals or ceramics, which make them valuable for applications in fields such as the aerospace and automotive industries. In this study, interpenetrating nanocomposites of three-dimensionally ordered macroporous (3DOM) tungsten-silicon oxycarbide (W-SiOC) were prepared, and their mechanical properties were investigated. In these nanocomposites, the crystalline tungsten and amorphous silicon oxycarbide phases both form continuous and interpenetrating networks, with some discrete free carbon nanodomains. The W-SiOC material inherits the periodic structure from its 3DOM W matrix, and this periodic structure can be maintained up to 1000 °C. In situ SEM micropillar compression tests demonstrated that the 3DOM W-SiOC material could sustain a maximum average stress of 1.1 GPa, a factor of 22 greater than that of the 3DOM W matrix, resulting in a specific strength of 640 MPa/(Mg/m3) at 30 °C. Deformation behavior of the developed 3DOM nanocomposite in a wide temperature range (30-575 °C) was investigated. The deformation mode of 3DOM W-SiOC exhibited a transition from fracture-dominated deformation at low temperatures to plastic deformation above 425 °C.

This article presents a compact model for the drain current and capacitances of hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs). The model is valid in the deep and tail states regions of operations, with a smooth transition between the two. The model parameters were extracted independently in the two regions using the unified model and extraction method (UMEM). The subthreshold regime and series resistances are considered for the drain current modeling. For the capacitances, it was found that the bias-dependent parasitic capacitances play a dominant role. The model was validated with TCAD simulations, with very good agreement.

Silicon heterojunction solar cells can employ p-type hydrogenated nanocrystalline silicon nc-Si:H(p) on their front side, since these can provide better transparency and contact resistance compared to hydrogenated p-type amorphous silicon layers. We investigate here the influence of trimethyl boron (TMB) and BF3 as dopant source on the layer properties and its performance in solar cells. Both gases enable high efficiencies but yield a different crystallinity and effective doping. A high BF3 flow lowers the series resistance through a low activation energy of dark lateral conductivity and maintains a high crystallinity. This allows fill factors up to 83%, however with the apparition of a parasitic absorption in the UV. A low TMB flow enables simultaneously a high crystallinity and a low activation energy. As an illustration of this layer potential, a 23.9%-certified efficiency is achieved with a 2 x 2 cm(2) screen-printed device. We finally suggest that similar transport versus transparency trade-offs can be reached for both dopant types for front junction application, while high BF3 flow allowing lower series resistance might be of interest when placed on the rear side.

Contemporary thin-film photovoltaic (PV) materials contain elements that are scarce (CIGS) or regulated (CdTe and lead-based perovskites), a fact that may limit the widespread impact of these emerging PV technologies. Tin halide perovskites utilize materials less stringently regulated than the lead (Pb) employed in mainstream perovskite solar cells; however, even today's best tin-halide perovskite thin films suffer from limited carrier diffusion length and poor film morphology. We devised a synthetic route to enable in situ reaction between metallic Sn and I2 in dimethyl sulfoxide (DMSO), a reaction that generates a highly coordinated SnI2·(DMSO)x adduct that is well-dispersed in the precursor solution. The adduct directs out-of-plane crystal orientation and achieves a more homogeneous structure in polycrystalline perovskite thin films. This approach improves the electron diffusion length of tin-halide perovskite to 290 ± 20 nm compared to 210 ± 20 nm in reference films. We fabricate tin-halide perovskite solar cells with a power conversion efficiency of 14.6% as certified in an independent lab. This represents a ∼20% increase compared to the previous best-performing certified tin-halide perovskite solar cells. The cells outperform prior earth-abundant and heavy-metal-free inorganic-active-layer-based thin-film solar cells such as those based on amorphous silicon, Cu2ZnSn(S/Se)4 , and Sb2(S/Se)3.

Silicon heterojunction (SHJ) solar cell technology has recently made great progress in mass production. In particular, the average power conversion efficiency (PCE) of mass-produced solar cells has reached nearly 24%. However, the low short-circuit current density (Jsc), a drawback of the SHJ solar cells, has become a bottleneck limiting its further efficiency breakthrough. Therefore, an effective light trapping method is urgently needed for mass-produced SHJ solar cells. In this work, an innovative stacked mask method is developed and combined with a two-step texturing (TST) method to prepare micro-pyramid structures on the front and back side of SHJ solar cells with different pyramid bottom angles, respectively. This asymmetrical structure fabricated through stacked mask method significantly improves the light trapping effect without negative influence on the surface passivation effect. The optical and electrical properties of the SHJ solar cells with this asymmetrical structure under the front side illumination are discussed in detail. It is concluded that the smaller the bottom angle of the backside pyramid, the thinner the amorphous silicon passivation layer is required and the better the surface passivation quality is obtained. The external quantum efficiency (EQE) results demonstrate that the best bottom angle of backside pyramids corresponding to the optimum light trapping effect for the front side illumination is about 16°, which is consistent with the simulation results of the ray tracer. As for the optimal asymmetric structure, the Jsc of the mass-produced SHJ solar cell is improved by 0.36 mA/cm2 and the PCE is increased over 24%.

Achieving low contact resistivity for the p contact in silicon heterojunction SHJ solar cells is challenging when classic n type transparent conductive oxides TCOs , such as indium tin oxide ITO , are used in the contact stack. Here, we report on SHJ solar cells with interdigitated back contact IBC and a direct aluminium Al metallisation applied to the p contact. We find that carefully annealing an Al a Si H p p type amorphous silicon contact at moderate temperatures leads to a specific contact resistivity that is half as low as its silver Ag ITO counterpart. This is explained by Al diffusing into a Si H p upon temperature treatment, forming a partially crystallised aluminium silicide layer. For a sufficiently high doping level in a Si H p , this enables an efficient tunnel recombination of holes from a Si H p to the Al contact. An estimate for this tunnelling dominated specific contact resistivity is calculated as a function of the interface doping density. Best fabricated IBC SHJ solar cells with Al p contact yield a fill factor of 77.5 and a power conversion efficiency of 22.3 . The main differences to devices with an Ag ITO a Si H p contact stack are a decrease in open circuit voltage by 14 mV and a slightly higher series resistance Rs . While the first aspect can be ascribed to increased interface recombination, the second one is unexpected and requires further investigation. Interestingly, omitting an intermediate TCO does not lead to current losses in devices with Al contacts, which is further investigated by optical simulations. Finally, electrical equivalent circuit simulations are conducted to describe the electrical behaviour of the investigated devices

In this paper, a new study has been carried out to analyze the behavior of four different Photovoltaic (PV) module technologies such as the Mono-crystalline silicon, the Multi-crystalline silicon, the amorphous silicon and the Telluride Cadmium as sub-systems from which a 400kWp pilot plant have been constructed at Ghardaia (The northern-central Sahara desert of Algeria). In this work, the results obtained from experimental data acquisition over a period of one year have been analyzed and discussed in terms of plant power production. In addition to that, performance indicators comprising the reference yield, the final yield, the performance ratio, the capacity factor and a newly suggested factor called the power ratio have been used to assess the sub-systems energetic performances. The performances of the studied sub-systems have been compared, then, to those of other systems located in countries regarded as having similar radiometric and climatic conditions. An additional study have been conducted to evaluate the effect of such important climatic and operating parameters as wind speed, ambient temperature, solar irradiance and module temperature on the energetic performances of the studied sub-systems. The experimental results obtained from monitoring of the studied sub-systems indicate that the plant performs best when it is operated under irradiance comprised between 5.56 kWh/m2 and 7.04 kWh/m2 and ambient temperature between 2 °C and 45 °C. Based on energy production and thermal stability results, the present study has allowed the identification of the most efficient and the best suitable of the aforementioned PV technologies for such arid-regions conditions.

Photovoltaic/thermal (PV/T) systems are taking up an increasing market share owing to a high overall solar energy efficiency. An innovative PV/T system that combines amorphous silicon cells and mic...

A maximum efficiency of 17% for ultra-thin n-type AZO layer and 17.5% for ultra-thin n-type TiO2 layer based silicon heterojunction solar cell is reported by optimizing its properties which is much higher than practically obtained efficiency signifying a lot of improvements can be performed to improve efficiency of TiO2/Si and AZO/Si heterojunction solar cell. AZO layer and TiO2 layer is used as n-type emitter layer and crystalline silicon wafer is used as p-type (p-cSi) layer for modelling AZO/Si and TiO2/Si heterojunctions solar cell respectively using AFORS HET automat simulation software. Various parameters like thickness of AZO, TiO2 layer, p-cSi layer, doping concentration of donors (Nd) and effective conduction band density (Nc) are optimized. Finally, texturing at different angle is studied and maximum efficiency is reported at 70 µm thick p-type crystalline Silicon (p-cSi) wafer, that can be very helpful for manufacturing low cost HJ solar cells at industrial scale because of thin wafer and removal of additional processing setup required for deposition of amorphous silicon i-layer. Utilization of TiO2 and Aluminium doped Zinc Oxide as n-type layer and p-cSi as p-type layer can help in producing low cost and efficient heterojunction (HJ) than compared to HJ with intrinsic thin layer HIT solar cells.

Monolithic 3-dimensional integration (M3D) requires heat treatment techniques that should not degrade the device performance of the lower layers when applied to device fabrication in the upper layers. Deep ultraviolet (DUV) laser annealing was implemented in the crystallization of amorphous silicon and source/drain junction activation to fabricate polycrystalline silicon (poly-Si) metal-oxide-semiconductor field-effect-transistors (MOSFETs) for upper-layer devices. The poly-Si MOSFET devices were fabricated successfully on top of the bottom electronic circuit layer (isolated by a thick silicon dioxide layer). Devices on the upper and lower layers were connected through interlayer vias to form a current-starved ring oscillator. The current-to-frequency converter on the bottom layer showed a reasonable increase in frequency as the current of the poly-Si MOSFET on the upper layer increased with increasing silicon grain size, confirming that DUV laser annealing did not degrade the performance of the bottom layer devices. This opens more opportunities for using DUV laser annealing in the M3D integration.