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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.

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.

This study draws on our experiences with graphene to perform a hybrid TCO structure composed of AZO and graphene. We first set out to enhance the electrical and optical properties of AZO to enable its use especially in the field of solar cell. Hence, in our study, we deposited various thicknesses of AZO thin films on glass substrates and transferred single layer graphene on them to realize the formation of hybrid TCO structure. Among the various AZO film thicknesses, the optimum one, 300 nm, was determined and then the graphene film was added on top of the AZO film. This hybrid structure was applied to the silicon-based heterojunction solar cell with the idea of improving the cell performance. The cell performance fabricated using AZO film and AZO + graphene structure was analyzed using solar simulator. Our findings highlight the fact that the presence of graphene improved the cell efficiency by about 7%. Our research was further extended using ITO and ITO + graphene hybrid structure as TCO for silicon-based solar cell. We discovered that graphene incorporation increased the cell efficiency by almost 12% based on our results with ITO + graphene hybrid TCO structure on a similar cell.

Ion implanted PERC cells have already achieved power conversion efficiencies of about 20.0%. The process flows reported in the literature for the ion implanted PERC cells with commonly utilized Al2O3/SiNx rear passivation stack, which has the benefit of being less sensitive to surface roughness than SiO2/SiNx stack passivation, notably suffer from the additional process steps such as single side polishing and single side protection. Here, we present a simplified process flow for the fabrication of ion implanted PERC cells having Al2O3/SiNx stack passivation at the textured rear surface without any rear side processing, leading to a power conversion efficiency of 20% at large area. In this context, we show the sensitivity of solar cell efficiency to firing peak temperature, implantation dose, and Al2O3 thickness. The results of the present research will provide a basis for high efficiency implanted PERC cells with significantly reduced workload and cost.

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.

In this work, the electrical and charge conduction characteristics of a contact structure featuring thermally evaporated MoOx, deposited on n- and p-type crystalline silicon (c-Si), are extensively investigated by room temperature current–voltage (I–V), transmission line measurements (TLM), and temperature-dependent current–voltage measurements (I–V–T). XRD diffraction spectrum shows that the deposited MoOx film exhibits amorphous nature. From TLM measurements, the values of contact resistivity are calculated to be $${\rho_{\rm {c}}}$$ : 55.9 mΩ-cm2 for Ag/MoOx/n-Si and $${\rho_{\rm {c}}}$$ : 48.7 mΩ-cm2 for Ag/MoOx/p-Si. The barrier parameters such as barrier height ( $${{\phi }_{\mathrm{e}}}$$ ) and ideality factor ( $${n}$$ ) are investigated by the thermionic emission theory for I–V and I–V–T measurements. The $${{\phi }_{\mathrm{e}}}$$ , $${n}$$ , and conventional Richardson plot demonstrate resolute temperature dependency, obeying the barrier height of Gaussian distribution model. The uniform barrier height values are calculated to be $${{\phi }_{\mathrm{b}}}$$ :1.24 eV for Ag/MoOx/n-Si and $${{\phi }_{\mathrm{b}}}$$ :0.66 eV for Ag/MoOx/p-Si from the extrapolation of $${{\phi }_{\mathrm{e}}}$$ at $${n}$$ $${=}$$ 1 of the linear fitting of the variation with the experimental barrier height $${{\phi }_{\mathrm{e}}}$$ with ideality factor. The activation energy ( $${{E}_{\mathrm{a}}}$$ ) and Richardson constant (A*), obtained from Richardson plot, are much smaller than $${{\phi }_{\mathrm{b}}}$$ and the theoretical values of n- and p-type c-Si. The modified Richardson plot yields more reliable Richardson constant and homogeneous barrier height values of 106.2 Acm−2 K−2 and 1.21 eV, 23.4 Acm−2 K−2 and 0.63 eV for Ag/MoOx/n-Si and Ag/MoOx/p-Si heterostructures, respectively. The results demonstrate that thermally evaporated MoOx has particular advantages due to its good rectifying characteristics such as the extra enhancement to barrier height and low contact resistivity for interfacial layer applications.

Passivated emitter and rear cell (PERC) concept with an already developed roadmap for 24% efficiency will be leading the photovoltaics industry in the upcoming years. In a few industrial pilot lines, efficiencies above 22% have already been attained. Pilot lines have important roles in bridging lab scale proven concepts with the products which are ready for mass production. Therefore, GUNAM Photovoltaic Line which is specialized on PERC concepts has been established to overcome the barriers that hinder the performance of c-Si solar cells in PERC concepts in a relevant environment. The aim of this article is to show how a loss analysis can be employed in a practical way in an industrially relevant environment. The analysis depends on the first results of the studies from 6 months ramp up period of GPVL A batch of standard PERC type solar cells with p-type base and atomic layer deposited Al2O3 rear passivation have been fabricated during the ramp up of the line. A detailed gain-loss analysis was performed to address the optical, electrical and recombination losses in order to increase the cell efficiency. (C) 2019 Elsevier Ltd. All rights reserved.

Performance of crystalline Silicon solar cells depends on numerous factors. One key factor is a surface structure which can restrict electrical and optical properties due to recombination of generated carriers and reflection of incident light. Surface texturing reduces reflection from a flat surface which increases absorption of light. Anisotropic alkaline etchants are commonly used for texturing mono-crystalline Silicon wafers which produce pyramid structures on the surface. Because of randomly oriented crystallographic grains, this method is not feasible for multi-crystalline Silicon wafers. Here, an alternative texturing process using a laser system is proposed. Laser beam creates vertical and horizontal grooves on the surface in which the intersections are for a light trapping purpose. Laser parameters are determined experimentally to have the lowest reflection. Next, chemical post-texture cleaning is performed to remove laser-induced damages and other residues. Finally, samples went through general solar cell fabrication steps. For characterizations, weighted reflection is measured and correlated with Scanning Electron Microscopy images of a textured surface to evaluate the performance of texturing and post-texture cleaning. To examine fabricated solar cells' performance, I–V curve and External Quantum Efficiency are measured. Results indicate that proposed processes lead to an improved efficiency compared to reference samples.

To a certain extent, the photovoltaics industry is well developed, and the performance and expected yield of standard photovoltaic modules are well documented and researched. However, newer more efficient photovoltaic cell and module technologies are being developed all over the world. Outdoor testing of new photovoltaic technologies is very important to understand and validate their reliability and performance under different environmental conditions. For the first time, one year of monitored performance data is presented and analyzed for two high efficiencies interdigitated back contact prototype mini-modules at different locations, having different climates. The test results of a commercial heterojunction with intrinsic thin-layer” module are also presented for comparison. The results showed that the two mini-modules remained stable for the duration of the test period, and showed no signs of degradation. They did perform significantly differently due to the different climatic conditions. The results also show that the combination of ambient temperature difference together with relative humidity impacts the performance of the modules. Calculated outdoor yearly efficiencies are 19.05% and 18.36% for two integrated back contact mini-modules tested in Petten-Netherland and Ankara-Turkey, respectively. The temperature coefficients of the modules are also calculated and compared with two commercial photovoltaic modules. © 2019 Elsevier Ltd

In this study, we investigated the impact of incorporating graphene with Ga-doped ZnO (GZO) when employing them as a TCO layer on Si-based solar cell. GZO thin films with various thicknesses (50-450 nm) were fabricated by the sputtering method using a single target. The aim here was to determine the GZO film with the optimum thickness to incorporate it with single layer graphene as TCO. This thickness was found to be 350 nm as that was the best crystalline quality found in the Opattern. Further, this sample had the lowest sheet resistance and highest transmission values as confirmed by electrical (sheet resistance), and optical characterizations (transmission). Topographic (SEM and AFM), electrical (resistivity and carrier concentration) measurements were also conducted on the same sample. The graphene film grown on copper in a CVD system was then transferred on top of this sample to fabricate the hybrid TCO structure. We found that graphene integrated GZO hybrid TCO film showed higher sheet resistance due to high sheet resistance of graphene and similar optical properties thanks to high optical transmission of graphene. Employing graphene-based TCO layer in the solar cell resulted in higher open-circuit voltage, consequently improving the conversion efficiency from 10.0% to 11.2%. (c) 2021 Elsevier Ltd. All rights reserved.

Dopant-free carrier-selective transition metal oxide (TMO) contacts offer unique electrical properties pertaining to the rectification of doping-related issues in silicon (cSi) solar cell. In this paper, cSi heterojunction solar cell featuring TMOs of molybdenum oxide (MoOx) and titanium oxide (TiOx) as hole- and electron-selective contacts, respectively, has been realized using Silvaco TCAD. The photovoltaic performance has been evaluated based on the electron affinity of TiOx, its thickness, interfacial charge density, band gap, and operating temperature. MoOx with an appropriate work function prompts band bending leading to Fermi level pinning at top interface. Insertion of TiOx with low electron affinity reduces the rear energy barrier against electrons from 0.86 eV to 0.15 eV. Minimum recombination has been observed for electron affinity values range of 3.6–4.2 eV. The rear interface defects (Dit) should be minimized to reduce the recombination and to facilitate transportation of electrons. The device numerically demonstrated Voc of 723 mV, Jsc 39.2 mA/cm2, FF 79.8%, and η of 22.64% with temperature coefficient of −0.08%/°C. These results validate the applicability of heterojunction design with fully-covered carrier-selective contacts that can be useful for industrial applications as it eliminates the need of doped layers with the associated capital-intensive and complicated fabrication processes.

A solar cell device, fabricated on high density array cylindrical pillars, enables photogenerated carrier collection in the radial direction, thus shortening the path length of the carriers reaching the junction. It also provides advantages over conventional planar junction solar cells, such as reduced surface reflectance and enhanced light trapping. In this study, highly ordered Si micropillars were fabricated by photolithography and metal assisted etching (MAE) methods. It is shown that the use of ethanol as a solvent during the etching process and increasing HF concentration in the MAE solution both improve the quality of the surfaces of the pillars. Micropillars with smooth sidewalls and a high aspect ratio were obtained in this way. Solar cells with a radial junction were then fabricated on these micropillars. Standard doping, SiO2/SiNx passivation, and metallisation steps were carried out for the fabrication of solar cells with different micropillar lengths. A significant decrease in reflectance values was observed as the micropillar length increased, as expected. Solar cell short circuit current density (Jsc) and efficiency (η) of the solar cells tended to increase with micropillar length up to 11.5 µm and then decrease due to increased surface recombination. The maximum efficiency achieved in this study is 17.26%.

In this paper, we present the results of the study on the fabrication of inverted pyramids on n-type Si wafer by a single-step anisotropic copper-assisted chemical etching. The relationship between etchant composition, etching time and the surface morphology for n-type Si has been investigated. Different surface structures were obtained by adjusting molarity of H 2 O 2 , Cu(NO 3 ) 2 , HF in the etching solution. Cu(NO 3 ) 2 amount promoted, while increasing H 2 O 2 amount over optimum value reduced the etch rate. By optimizing etching duration, etching temperature and etchant composition, uniform distribution of inverted pyramids with dimensions around 2 μm was achieved. Surface average weighted reflectance was reduced to 5.67% in the wavelength range of 400-1000 nm with novel surface texturing method.

Surface texturing is one of the key process steps in solar cell fabrication. For an ideal surface texturing, surface recombination should be kept as low as possible while the light trapping property is improved. The formation of a random inverted pyramids is a good candidate with its improved light trapping properties compared to standard upright pyramid texturing and its reduced surface roughness compared to nanowire texturing resulting in reduced surface recombination velocity. In this work, we investigate a single step, lithography-free, Cu-assisted inverted pyramid texturing resulting in significantly reduced surface reflection on p-type Cz-Si. With the help of randomly distributed star-shaped inverted pyramid texturing on p-type Si, the weighted average reflection was reduced to 3% for p-type Si between 400-1000 nm. As a first cell trial, standard Al-BSF cells were fabricated using industrial process tools on p-wafer with star-shaped IPs. The low-cost, effective and repeatable nature of the developed single-step etching process has a high potential to replace surface texturing steps in the large-scale solar cell production cycle. Due to the implantation of star-shaped inverted pyramids to Al-BSF Si solar cell fabrication, short circuit current density was improved by more than 3.5%, resulting in 39.1mA/cm2.

Impurities are of crucial interest in optoelectronic devices as they affect carrier lifetimes and electrical properties. In view of that, it is important to incorporate certain processing steps to reduce impurities effect on final devices. The aim of this work is to enhance silicon carbide SiC purity for silicon passivation. Low cost method of SiC purification is presented. This method combines three main steps consisting of formation of porous silicon carbide layers by acid vapor etching followed by a photo-thermal annealing at different temperatures. Finally, obtained SiC powder was subject to a chemical treatment to remove porous SiC layer. Effect of gettering temperature on purification efficiency was evaluated by inductively coupled plasma atomic emission spectrometry (ICP-AES). The gettering experiment was performed at 800–950 °C, and optimum results were obtained at 950 °C. SiC purity is improved from 3 N (99.977%) to 5 N (99.999%) with an impurity removal efficiency of 96.56%. Purified SiC was used as a target to synthesize SiC layers using pulsed laser deposition technique (PLD) for optoelectronic devices. The use of intrinsic amorphous silicon carbide (a-SiC) passivating layers was investigated especially by photoconductivity decay technique. Improved SiC target purity leads to a significant enhancement of a-SiC passivating properties attributed to the surface recombination velocity decrease. Electrical properties of a-SiC/c-Si(p) were also studied using I-V and C-V techniques.

Contacts featuring multiple layers of materials in combination with metal electrodes enabled record-high power conversion efficiencies for solar cells in recent years. Minimizing the contact resistivity in these multilayer structures is critical to achieve a high device performance and rapid characterization methods are crucial for the experimental analysis of this aspect. However, commonly used test methods and the associated mathematical formulations to extract contact resistivity are not designed for samples with multiple layers. In this work, we analyze formulations describing the resistance measured in ohmic multilayer test structures, which are used to fit and extract an unknown contact resistivity. We focus on a contacting scheme with circular electrodes, commonly named after Cox and Strack (CS), and analyze a material configuration consisting of a thick Si substrate fully coated with a thin conductive layer (CL). We demonstrate the applicability and accuracy of various spreading resistance models (SRMs) from the literature to calculate the measured resistance and compare the results with those obtained by the finite element method (FEM). Moreover, we present a new SRM with a closed-form expression for the measured resistance, which is computationally more efficient than the existing SRMs. Last, we demonstrate the applicability of this model in experiments with (n)c-Si/(i)a-Si:H/(n)a-Si:H/indium tin oxide (ITO) test structures.

Crystalline-Si (c-Si) based solar cells (SC) efficiency remains one of the most challenging part in photovoltaic industry. Besides of the thermodynamical limits, the optical losses due to indirect band-gap structure of the material require additional treatment which known as a photonic design of the SC surface [1] . Numerous manipulations are performed to increase the efficiency of commercial solar cells. In most of these methods, the main concept is increasing light interaction by the cell through chemical modification of the morphology of the surface. Creation of pyramid-like structure on SC surface through the chemical etching by KOH solution is the most common industrial method nowadays. Recently we proposed Nonlinear Laser Lithography (NLL) as an alternative method for the traditional chemical etching [2] . The method is based on the well known phenomenon Laser Induced Periodic Surface Structuring (LIPSS), allowing creation of wellordered, periodic ablation and/or oxidation lines on the material surface with subwavelength period under ultrashort pulse laser illumination. In comparison with the traditional chemical treatment, the method is cheap, single-step and chemically free. However, the damage of the crystalline structure of the SC surface during ablation limiting the final efficiency of the device. In the current work, we demonstrate the new achievement in the efficiency of c-Si solar cell based on NLL treated surface. By proper design of the laser parameters and the scanning geometry during the NLL process, as well as proper post-passivation of the SC surface, we demonstrate more than 16% efficiency of the final device. To the best of our knowledge, this is the highest efficiency demonstrated so far on a laser treated c-Si solar cell without any chemical texturing.

Dielectric colloidal nanospheres (NSs) are promising candidates for light management in photonic devices such as solar cells (SCs). NS arrays can direct the broad incident solar radiation into a set of tighter foci, at which light intensity becomes considerably concentrated, enabling higher photovoltaic conversion efficiency. Furthermore, the NS arrays acting as an effective medium on the SC surface can reduce reflectance and facilitate improved forward scattering. Therefore, uniform arrays of NSs located on top of the SC can behave as antireflection coatings or as microlenses, which can be regarded as a surface distributed light concentrator within the framework of concentrated photovoltaics. Fabrication of NS‐based light‐trapping structures is low‐cost and less complicated than common alternatives such as vacuum evaporated multilayer antireflection coatings. In this work, experimental demonstration and computational confirmation on the shape adjustment of such NS structures for improved light harvesting and efficiency enhancement in Si SCs are studied. The light conversion efficiency of Si solar cells is shown to improve by more than 27% with shape adjustment of NS arrays.

Enhancement of the conversion efficiency of silicon solar cells is crucial for the improvement of renewable electricity resources. The device properties such as minority carrier lifetime, series resistance, contact resistance and optical properties should be improved simultaneously to achieve higher photo conversion efficiencies. We use industry compatible processes flow to fabricate large-area silicon heterojunction (SHJ) solar cells combined with reactive ITO sputtering. The passivation properties of a-Si:H layer was improved by hydrogen plasma treatment resulting in a lower interface defect density and higher “H” content in the deposited thin a-Si:H layer. Moreover, carrier density, mobility and resistivity of ITO layer was analyzed and the best deposition condition of ITO is integrated to SHJ solar cell process sequence. Contact resistivity between ITO and low temperature silver paste was decreased by optimized drying and curing temperature parameters. In large-area SHJ solar cell, we have achieved conversion efficiency of 20.8%.

Thin film solar cells are an exciting topic for low cost and high efficient solar cells. Owing to the high price of the indium metal in the fabrication of copper indium gallium diselenide (CIGS) solar cells, Cu2ZnSn(SSe)(4) thin films are used as a new material to reduce the cost and increase the efficiency. As an alternative absorber material for solar cell production, Cu2ZnTi(S:Se)(4) thin films were deposited by the co-sputtering method at various temperatures. During the deposition, Cu, ZnSe and Ti targets were used as metal sources. The Cu2ZnTi(S:Se)(4) thin films were annealed in H2S:Ar (1:9) atmosphere. The morphological, structural and optical properties of Cu2ZnTi(S:Se)(4) thin films was analyzed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) Raman spectroscopy and UV-Vis-NIR spectrometer. It was seen that the thin films had good optical absorption till the infrared region and the band gap of the Cu2ZnTi(S:Se)(4) thin films were smaller than the conventional Cu2ZnSnS4 thin films. Furthermore, fabrication of a solar cell with 1.96% power conversion efficiency was reported using a Cu2ZnTi(S:Se)(4) thin film as a low cost absorber layer. (c) 2019 Elsevier Ltd. All rights reserved.

WOS: 000434647100009, Gold-induced (Au-) crystallization of amorphous germanium (-Ge) thin films was investigated by depositing Ge on aluminum-doped zinc oxide and glass substrates through electron beam evaporation at room temperature. The influence of the postannealing temperatures on the structural properties of the Ge thin films was investigated by employing Raman spectra, X-ray diffraction, and scanning electron microscopy. The Raman and X-ray diffraction results indicated that the Au-induced crystallization of the Ge films yielded crystallization at temperature as low as 300 degrees C for 1hour. The amount of crystallization fraction and the film quality were improved with increasing the postannealing temperatures. The scanning electron microscopy images show that Au clusters are found on the front surface of the Ge films after the films were annealed at 500 degrees C for 1hour. This suggests that Au atoms move toward the surface of Ge film during annealing. The effects of annealing temperatures on the electrical conductivity of Ge films were investigated through current-voltage measurements. The room temperature conductivity was estimated as 0.54 and 0.73Scm(-1) for annealed samples grown on aluminum-doped zinc oxide and glass substrates, respectively. These findings could be very useful to realize inexpensive Ge-based electronic and photovoltaic applications., Center for Solar Energy Research and Applications (GuNAM) at Middle East Technical University, The authors acknowledge the Center for Solar Energy Research and Applications (GuNAM) at Middle East Technical University.

Here, the authors studied a silicon-germanium (Si1-xGex) absorber layer for the design and simulation of an ultra-thin crystalline silicon solar cell using Silvaco technology computer-aided design. Seeking ways to design and fabricate solar cells using 100m thicker silicon substrates is the subject of intense research efforts among the photovoltaic (PV) community. The aim is to further reduce the substrate thickness to 20m without compromising the efficiency of the solar cell. A thin layer of SiGe film with the Ge composition of 15% has been introduced in this work that assists in absorbing the longer wavelength of the sunlight spectrum. The effects of the doping concentration and absorber layer thickness on the conversion efficiency have been examined. The simulated results exhibited significant enhancement in the sunlight absorption as compared to the reference structure based on crystalline silicon. The highest efficiency of 16.8% with an overall solar cell thickness of approximate to 26m has been observed. The proposed heterostructure solar cell design will support the industrial development of an efficient, low-cost, shorter energy payback time, and light-weight PV technology for its widespread implementation.

Light-induced electroless plating (LIEP) is an easy and inexpensive method that has been widely used for seed layer deposition of Nickel/Copper (Ni/Cu)-based metallization in the solar cell. In this study, material characterization aspects of the Ni seed layer and Ni silicide formation at different bath conditions and annealing temperatures on the n-side of a silicon diode structure have been examined to achieve the optimum cell contacts. The effects of morphology and chemical composition of Ni film on its electrical conductivity were evaluated and described by a quantum mechanical model. It has been found that correlation exists between the theoretical and experimental conductivity of Ni film. Residual stress and phase transformation of Ni silicide as a function of annealing temperature were evaluated using Raman and XRD techniques. Finally, transmission line measurement (TLM) technique was employed to determine the contact resistance of Ni/Si stack after thermal treatment and to understand its correlation with the chemical-structural properties. Results indicated that low electrical resistive mono-silicide (NiSi) phase as low as 5 mΩ.cm2 was obtained.

Surface texturing of transparent conductive oxides is crucial to improve the fraction of incident light trapped in the absorber layer of thin film silicon based solar cells to improve the device performance. In this work, we fabricate and compare periodic, overlapping, and random surface textures and patterns on aluminium doped zinc oxide (AZO) using direct laser processing. The effects of the used laser wavelength, laser operating frequency, and pulse periodicity on the structural, morphological, and optical response of the AZO films were investigated. By optimizing the laser parameters and the associated process conditions, a drastic increase up to 60% in the transmittance haze over the entire solar was achieved.

Extraction of contact resistivity (pc) with the four-point probe (4PP) method requires considerably fewer fabrication and measurement steps compared to conventional alternatives (e.g. the transfer length method, TLM). Yet, the method is rarely used, mainly due to the requirement of 3D simulations used in the data fitting procedure. Moreover, a work analyzing the details of the method, which can provide a quantitative guideline to the users, is lacking in the literature. In this work, we show that the 3D simulations can be replaced with a spreading resistance model (SRM) implemented in a numerical calculation platform (e.g. MATLAB). Using the SRM, we achieve drastically short calculation durations (

The aluminum induced texturing method offers an effective light trapping scheme by random texture that is formed by U-shaped craters on the glass surface. The texture is mainly shaped by the reaction between Al and SiO2. However, the reaction mechanism is not totally understood. Besides, the influence of other components present in the glass such as Na2O, CaO, and MgO. is neglected. In this study, the evolution of Al films on soda-lime glass during annealing has been inspected by depth resolved X-ray photoelectron spectroscopy. The elemental distribution of Si, Al and O have been investigated for different annealing durations and compositional analysis has been conducted for Na, Ca and Mg in addition to Si, Al and O. According to results, a relevant evolution model for annealing process has been constructed. © 2017 Elsevier B.V., Ministry of Education, Science and Technology: 0392.STZ.2013-2, This works was financially supported by the Ministry of Science and Technology of Turkey under SAN-TEZ program with the project number 0392.STZ.2013-2 . The authors are grateful to Türkiye Şişe ve Cam Fabrikaları A.Ş. for their support on this work and Dr. Tahir Çolakoğlu of METU for his helps.

In this work, we demonstrate a strong correlation between crystalline silicon (cSi) base doping concentration and the performance of cSi/MoO x heterojunction solar cell by investigating the structure numerically based on Silvaco TCAD simulation tool and experimentally. The doping concentration of n-type cSi was scanned in the 1 × 10 15 – 2 × 10 16 cm -3 range. Simulation results show that utilizing highly doped cSi wafer degrades the conversion efficiency of cSi/MoO x solar cell. Efficiency of 11.16% has been obtained from simulation results for 1 × 10 15 cm -3 doping concentration while this value reduces to less than 4% for wafer with a doping concentration of 2 × 10 16 cm -3 . These simulation results were demonstrated experimentally and n-type cSi wafers with two different doping concentrations were considered, 1 × 10 15 and 5.5 × 10 15 cm -3 . The key concept underlying this work is to differentiate explicitly the effect of cSi doping concentration on the performance of cSi/MoO x cell, thus a simple cell design is considered where n-type cSi wafers were heavily phosphorous-doped to form (n + ) at the front of the Si and thermally evaporated MoO x films with various thicknesses (

Cu2ZnTiS4 thin films have been deposited on glass by the reactive cosputtering technique with high-purity ZnS and Cu and Ti metals as targets and H2S as reactive gas. Cu2ZnTiS4 thin films were obtained at various temperatures and H2S flows and were annealed in H2S atmosphere. The structural, morphological, and optical properties of the Cu2ZnTiS4 thin films were examined by scanning electron microscopy, energy-dispersive spectroscopy, x-ray diffraction (XRD) analysis, and ultraviolet-visible (UV-Vis) spectroscopy. Agglomeration was found to increase with increasing temperature. The XRD peaks of the Cu2ZnTiS4 thin films were consistent with those of Cu2ZnSnS4. Furthermore, the optical bandgaps of the Cu2ZnTiS4 films were lower than those of conventional Cu2ZnSnS4 thin films.

Long term outdoor testing of the PV systems at different climatic conditions or different systems under the same ambient conditions are extremely important in producing policies for the transition to renewables. The present research is the testing of three different PV systems under the same climatic conditions of central Anatolia, after four years of operation. The systems consist of a mono-Si, an a-Si thin film and a CdTe thin film arrays. Different calculation procedures of the input solar irradiation on tilted surface are used for comparison. Performances together with degradation rates are computed using different procedures and also using the measured solar data of 20 km away from the installed systems. The accuracy is verified using 4 months of simultaneous measurements. The results showed that the aforementioned different input calculation procedures of the performances are important and determinant. The 44-months-average efficiencies of these three systems are calculated to be 11.86%, 6.40% and 5.30%, respectively. The degradation rates of these systems are obtained as 0.40%, 1.88% and 10.60%, respectively. Although the degradation rates that are calculated for the first two systems are quite similar to those appeared in the literature, CdTe system is considerably higher than those given in the literature.

WOS: 000390072700033, We demonstrate the fabrication of nano-sized surface textured crystalline silicon by a metal-assisted electroless etching method with nitric acid added as the hole injection agent. This method generates randomly shaped cone-like structures that offer a clear advantage over nanowires by enabling straightforward passivation with standard techniques. Average reflection values as low as 3% have been achieved. Optimizing the thickness of anti-reflective coatings, the doping depth and the screen-printed metal firing process increases the short circuit current of the cell by 0.82 mA/cm(2) over the reference cells, which had a pyramidal texture without nano texturing.

Losses caused by the metal top contacts still remain as an issue in crystalline silicon (Si) solar cells. One approach to eliminate shading losses is to utilise transparent nanostructure networks synthesised through rapid and low cost processes. In this work, the potential of highly conductive silver nanowire (Ag NW) networks as transparent top electrodes for the elimination of metallisation process in Si solar cells was investigated. Ag NW top contact cells were found to possess enhanced conversion efficiencies with respect to conventional metal contact reference cells. Increase in conversion efficiency was attributed to the elimination of shading losses, preferential scattering of light into the substrate by localised surface plasmon resonances (LSPRs) of the Ag NWs and localised and higher charge collection capability with respect to conventional metal contacts.

WOS: 000388085800053, We have investigated the relationship between structural and electrical properties of Ge thin films deposited on single crystal silicon (100) substrates by electron beam evaporation at room temperature. Post-thermal annealing was applied to obtain poly-crystalline Ge thin films. The structural effects of the annealing temperature and annealing time on the crystallization of Ge films were analyzed using Raman and X-ray diffraction measurements. Raman and X-ray diffraction spectra revealed a structural evolution from amorphous to crystalline phase with increasing annealing temperature and annealing time. It was found that high quality poly-crystalline Ge films were obtained with crystallization ratio of 90% at an annealing temperarure of 500 degrees C following the crystallization threshold of 450 degrees C. Effects of structural ordering on the electrical properties were investigated through current-voltage characteristics of fabricated heterostructure devices (Ge/p-Si). Smooth cathode-anode interchange in the diode behavior has been clearly observed following the structural ordering as a function of annealing temperature in a systematic way. These outcomes could be exploited for engineering of low-cost Ge based novel electronic and opto-electronic devices.

Light trapping is essential for thin film solar cells to decrease the solar electricity cost. Aluminum induced texturing (AIT) is an alternative and effective method for light trapping. Various parameters effects the final surface morphology in AIT. However, surface morphology obtained by AIT method on glass is mostly formed in annealing process which occurs at temperatures above 500 °C. In this study, annealing process under N 2 ambient is investigated. A relevant model of evolution is formed. In addition, diffusion of Na during this process is covered.

In this work, the electron-carrier-selectivity of ALD deposited TiO2 contact on n-type and p-type c-Si wafers is presented. The optical, compositional, and diode quality dependence of TiO2 on the ALD deposition temperature were analyzed using spectroscopic ellipsometry, AFM, XPS, GI-XRD, and CV measurements. By optimizing the ALD process parameters, an impressive effective minority carrier lifetime of up to 2.3 milliseconds corresponding to an iVoc of ~700 mV was obtained from wet chemical oxide-SiO2/TiO2 passivation stack layers. Finally, the asymmetry in C-V and J-V measurements betweenTiO2/n-type and TiO2/p-type c-Si heterojunctions was examined and the electron transport selectivity of TiO2 was revealed.

In this work, characteristics of silicon-based p$^{+\, }$type, intrinsic (I), n$^{-}$ type (Si-PIN) photodiodes with active area of 3.5 $\times $ 3.5 mm$^{2}$, 5.0 $\times $ 5.0 mm$^{2}$, or 7.0 $\times $ 7.0 mm$^{2}$ and their possible usage in optoelectronics were studied. The devices were fabricated in the Radiation Detector Application and Research Center (NÜRDAM) of Bolu Abant İzzet Baysal University, Turkey. To acquire the device specifications, the current-voltage (I-V) and the capacitance-voltage (C-V) measurements were carried out in the photoconductive mode. Quantum efficiency and spectral responsivity measurements were performed in the photovoltaic mode. Both measurements were carried out in a dark environment at room temperature. The measured values of the dark current (I$_{dc})$ and the capacitance of photodiodes were -6.97 to -19.10 nA and 23 to 61 pF at -5 V, respectively. The quantum efficiency measurements of the devices increased up to 66%. P responsivity was found to be 0.436 $\pm $ 1 mA/W at 820 nm. The results indicate that the I$_{dc}$ current and the performance of the devices were improved. Therefore, the devices can be utilized for optoelectronics applications and commercial usage.

WOS: 000485256900018 Aluminium induced crystallization (AIC) technique can be used to form the high-quality and large-grained polycrystalline silicon (poly-Si) thin films, which are with the thickness of similar to 200 nm and used as a seed layer, on silicon nitride coated glass substrate. Thanks to aluminium metal in AIC process, the natural doping of AIC thin films is p(+) type (similar to 2 x 10(18) cm(-3)). On the other hand, recombination of carriers can be controlled by partial doping through the defects that may have advantages to improve the thin film quality by the overdoping induced passivation. In this study, boron (B) and phosphorus (P) doped AIC seed layers were thicken to similar to 2 mu m by solid phase epitaxy (SPE) technique at 800 degrees C for 3 h under nitrogen flow in a tube furnace. During the crystallization annealing, exodiffusion of dopants was formed through the SPE film from the AIC seed layer. Optical microscope and electron back scattering diffraction technique (EBSD) were used to analyse the structural quality of the Si films. The poly-Si layer with an average grain size value of similar to 32 mu m was formed by AIC + SPE technique for P doped samples while EBSD analysis gave no results for B doped samples due to the quite deterioration on the surface of the films. AIC + SPE films were analyzed in terms of structural properties by using micro-Raman Spectroscopy and X-ray diffraction systems. The results showed that the crystallinity of compressive stress formed AIC + SPE films reached up to 98.55%. Additionally, the Raman analysis pointed out that no temperature-induced stress were generated in the AIC + SPE films while compressive stress was induced by increasing the annealing duration for doped AIC film. For all samples, the preferred orientation was < 100 >, and the crystallite size up to 44.4 nm was formed by phosphorus doping of AIC films. The doping efficiency was determined by time-of-flight secondary ion mass spectroscopy for doped samples. A graded n(+)n doping profile was obtained by exo-diffusion of phosphorus from the overdoped seed layer during the epitaxial thickening while boron doping of SPE film has failed with exo-diffusion of boron from AIC seed layer into SPE film. Finally, high-quality n(+)n type poly-Si films were fabricated on glass substrate by using AIC + SPE technique. TUBITAKTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [112T084]; Scientific Research Project Fund of Duzce UniversityDuzce University [2017.05.02.623] This work has been funded by TUBITAK under the project number 112T084 and the Scientific Research Project Fund of Duzce University under the project number 2017.05.02.623.

Radial junction solar cell is proposed as an alternative device geometry to planar junction solar cell due to its superior electro-optical performance. In this geometry, densely-packed micropillars enable the collection of minority carriers in the radial direction. Thus, the distance that carriers should travel to reach the p-n junction is shortened, allowing the use of low quality materials with poor carrier lifetime. In this study, we have experimentally studied the advantage of radial junction approach in low quality Si. For this purpose, we fabricated planar and radial junction solar cells using Si wafers with Au impurities. Average efficiency values of 15.74% and 15.66% were obtained for planar and radial cells in uncontaminated samples, respectively, indicating that close efficiency values were obtained when using high quality materials. However, in the case of contamination, the efficiency of the cells with radial junction degraded less compared to the planar junction with the values of 14.71% and 12.72%, respectively. This is consistent with the expectation that radial junction cells are less sensitive to the quality of the material used. Moreover, these results, together with future structural optimization, lay a solid foundation for lowering fabrication costs without reducing the performance of the solar cell. (C) 2019 Elsevier Ltd. All rights reserved.

Thin films of molybdenum oxide (MoOx) were fabricated by radio frequency (RF) reactive magnetron sputtering technique with various oxygen flow rates and the deposition pressure fixed at 4 mTorr. The stoichiometry, composition, chemical binding energy, electrical, and optical properties of the sputtered MoOx films were examined. The deposited films were characterised by x-ray photoelectron spectroscopy (XPS), capacitance-voltage measurement (CV), spectroscopic ellipsometer (SE), and ultraviolet-visible spectroscopy (UV-VIS). XPS studies of the film indicated the presence of Mo5+ and Mo6+ oxidation states within the film. The deposited sputtered films were semiconducting in nature with the highest work function of 5.92 eV observed for MoOx. The stoichiometry for RF sputtered MoOx (x < 3) was found to be 2.73. CV analysis indicated that density of defect states in the MoOx films decreased with the corresponding increase in the oxygen flow rate. SE studies have shown that the refractive indices of the as-deposited films ranged from -1.8-2.05 at nominal wavelength of 632.8 nm. Similarly, high transmittance and large band gap values of sputtered MoOx were observed. It was proved that deposited MoOx is of n-type character with the Fermi level variation observed within the band gap of MoOx upon changing the oxygen flow rate.