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Faormamadinium based perovskites have been proposed to replace the methylammonium lead tri-iodide (MAPbI3) perovskite as the light absorbing layer of photovoltaic cells owing to their photo-active and chemically stable properties. However, the crystal phase transition from the photo-active α -FAPbI3 to the non-perovksite δ -FAPbI3 still occurs in un-doped FAPbI3 films owing to the existence of crack defects, which degrads the photovoltaic responses. To investigate the crack ratio (CR)-dependent structure and excitonic characteristics of the polycrystalline FAPbI3 thin films deposited on the carboxylic acid functionalized ITO/glass substrates, various spectra and images were measured and analyzed, which can be utilized to make sense of the different devices responses of the resultant perovskite based photovoltaic cells. Our experimental results show that the there is a trade-off between the formations of surface defects and trapped iodide-mediated defects, thereby resulting in an optimal crack density or CR of the un-doped α -FAPbI3 active layer in the range from 4.86% to 9.27%. The decrease in the CR (tensile stress) results in the compressive lattice and thereby trapping the iodides near the PbI6 octahedra in the bottom region of the FAPbI3 perovskite films. When the CR of the FAPbI3 film is 8.47%, the open-circuit voltage (short-circuit current density) of the resultant photovoltaic cells significantly increased from 0.773 V (16.62 mA cm−2) to 0.945 V (18.20 mA cm−2) after 3 d. Our findings help understanding the photovoltaic responses of the FAPbI3 perovskite based photovoltaic cells on the different days. [ABSTRACT FROM AUTHOR]

The fabrication of quantum well solar cells with surface photonic crystal (SPC) and embedded photonic crystal (EPC) structures has resulted in solar cells with improved properties. When compared to reference solar cells (RSCs), the photoluminescence (PL) intensities of SPC solar cells and EPC solar cells have been enhanced by 89% and 114%, respectively. This indicates improved light absorption and emission characteristics in the presence of the periodic patterns (PCs). The short-circuit current (Isc) of EPC solar cells is 31% higher than that of RSCs, suggesting improved light absorption and carrier generation. On the other hand, SPC solar cells exhibit a 6% higher Isc compared to RSCs, and the open-circuit voltage has increased simultaneously. The fill factors (FF) of the solar cells are 84% for RSCs, 86% for SPC solar cells, and 76% for EPC solar cells. The higher FF in SPC solar cells suggests improved charge carrier collection efficiency. In terms of photoelectric conversion efficiency, SPC solar cells demonstrate a 10.6% increase, while EPC solar cells show a 7.7% increase. These improvements indicate that the incorporation of PCs in the solar cells enhances their ability to convert light into electrical energy. These findings highlight the potential of photonic crystals engineering for enhancing the performance of solar cells. [ABSTRACT FROM AUTHOR]

Hydrovoltaic devices (HDs) based on silicon nanowire (SiNW) arrays have received intensive attention due to their simple preparation, mature processing technology, and high output power. Investigating the impact of structure parameters of SiNWs on the performance of HDs can guide the optimization of the devices, but related research is still not sufficient. This work studies the effect of the SiNW density on the performance of HDs. SiNW arrays with different densities were prepared by controlling the react time of Si wafers in the seed solution (t seed) in metal-assisted chemical etching. Density of SiNW array gradually decreases with the increase of t seed. HDs were fabricated based on SiNW arrays with different densities. The research results indicate that the open-circuit voltage gradually decreases with increasing t seed, while the short-circuit current first increases and then decreases with increasing t seed. Overall, SiNW devices with t seed of 20 s and 60 s have the best output performance. The difference in output performance of HDs based on SiNWs with different densities is attributed to the difference in the gap sizes between SiNWs, specific surface area of SiNWs, and the number of SiNWs in parallel. This work gives the corresponding relationship between the preparation conditions of SiNWs, array density, and output performance of hydrovoltaic devices. Density parameters of SiNW arrays with optimized output performance and corresponding preparation conditions are revealed. The relevant results have important reference value for understanding the mechanism of HDs and designing structural parameters of SiNWs for high-performance hydrovoltaic devices. [ABSTRACT FROM AUTHOR]

High temperature superconducting (HTS) cable represents a promising solution for fulfilling the power demands of cities with large loads and high density. However, due to their connection to the distribution network, HTS cables are vulnerable to fault currents exceeding ten times their rated current, which poses a serious threat to both the safety of the cable and the operation of the grid. Considering the highly nonlinear nature of superconducting conductivity, this study develops a field–circuit coupling model to investigate the transient characteristics of distribution networks incorporating superconducting cables (DNSC). Firstly, a finite element model based on the two-dimensional H formulation was built to calculate the electrical and thermal parameters of the HTS cable. Subsequently, an equivalent circuit model of the distribution network was employed to estimate the short-circuit currents. Communicating via a co-simulation server, the superconducting cable current and distribution network impedance were updated in each step. Further, based on an actual DNSC system in Shenzhen, China, the highest quenching temperature of the cable and the maximum fault current of busbars were assessed. Finally, by integrating current limiters into the system, the withstand capability of the cable and busbars was determined, which indicates that the improved protection configuration can effectively suppress fault currents and ensure safe operation. Successfully applied to an actual distribution network, the co-simulation model utilizing the field–circuit coupling method addresses the challenges of solving highly nonlinear and time-varying systems, enabling transient analysis and protection research for the integration of superconducting devices into the conventional grid. [ABSTRACT FROM AUTHOR]

Vacancy-ordered double perovskites (A2BX6) have recently received impressive attention for photovoltaic applications, and the compound K2SnBr6 has desirable features for use in solar cells in such a way that it exhibits direct bandgap behaviour with dispersed band edges. However, the large bandgap value limits its use in higher-efficiency solar cells. Therefore, we have carried out exploratory research by analysing the photovoltaic effect of K2SnBr6 by tuning its bandgap with cation and anion substitutions. We studied the properties of K(2− y)RbySnBr(6− x)I x and K2Sn(1− z)Ti z Br(6− x)I x compounds to explore the photovoltaic effect by gradual substitution of Rb+, Ti4+ and I−1 for K+, Sn4+ and Br−1, respectively. Our density functional calculations in the monoclinic ground state crystal structure with the space group P 121 /n revealed that the K(2− y)Rb y SnBr(6− x)I x compounds considered in this study exhibit direct bandgap behaviour with well-dispersed band edges. Moreover, the bandgap value decreases as a function of the Rb and I concentrations. In addition to the low charge carrier effective mass, low excitonic binding energy values and low recombination rate, these compounds exhibit comparatively greater absorption coefficients in the visible range. The charge carrier transport properties, such as carrier mobility, carrier relaxation time, carrier diffusion coefficient and carrier diffusion length, are also seen in higher ranges for these Rb- and I-substituted compounds when compared to the parent compound. In addition, we have calculated the open-circuit voltage, fill factor, short-circuit current and power conversion efficiency for each compound. From the calculations and analysis, we observed that Rb and I substitution in K2SnBr6 increases the photovoltaic effect, and thus K(2− y)Rb y SnBr(6− x)I x compounds may be employed as absorbing layers in higher-efficiency solar cells. [ABSTRACT FROM AUTHOR]

The synergistic effect of high-quality NiO x hole transport layers (HTLs) deposited by ion beam sputtering on ITO substrates and the Ti3C2T x MXene doping of CH3NH3PbI3 (MAPI) perovskite layers is investigated in order to improve the power conversion efficiency (PCE) of p-i-n perovskite solar cells (PSCs). The 18 nm thick NiO x layers are pinhole-free and exhibit large-scale homogeneous surface morphology as revealed by the atomic force microscopy (AFM). The grazing-incidence x-ray diffraction showed a 0.75% expansion of the face-centered cubic lattice, suggesting an excess of oxygen as is typical for non-stoichiometric NiO x. The HTLs were used to fabricate the PSCs with MXene-doped MAPI layers. A PSC with undoped MAPI layer served as a control. The size of MAPI polycrystalline grains increased from 430 ± 80 nm to 620 ± 190 nm on the doping, as revealed by AFM. The 0.15 wt% MXene doping showed a 14.3% enhancement in PCE as compared to the PSC with undoped MAPI. The energy-resolved electrochemical impedance spectroscopy revealed one order of magnitude higher density of defect states in the band gap of MXene-doped MAPI layer, which eliminated beneficial effect of reduced total area of larger MAPI grain boundaries, decreasing short-circuit current. The PCE improvement is attributed to a decrease of the work function from âˆ'5.26 eV to âˆ'5.32 eV on the MXene doping, which increased open-circuit voltage and fill factor. [ABSTRACT FROM AUTHOR]

To investigate the influence of thiophene-fused indanone or thieno[3,2- b ]thiophene-fused indanone on acceptors, we designed and synthesized three molecules BTP-CC, BTP-TTC and BTP-TC. Impressively, a high open-circuit voltage (V oc) of 0.98 V was achieved in BTP-CC based device, which is one of the highest values based on A-DA′D-A type acceptors to date. The small Î" E HOMO (0.05 eV) between PBDB-T and BTP-TTC resulted in the inefficient exciton dissociation and charge transfer. Despite obtaining a relatively high V oc of 0.95 V, BTP-TTC based organic solar cell (OSC) displayed poor short-circuit current density (J sc) and efficiency. Compared with BTP-CC and BTP-TTC, BTP-TC exhibited red-shifted absorption and down-shifted energy levels. Benefiting from the increased crystallinity and the stronger intermolecular interaction, the device of PBDB-T:BTP-TC achieved improved charge dissociation, enhanced charge transport and suppressed charge recombination. Eventually, BTP-TC based OSC realized a higher efficiency of 13.57% with V oc of 0.86 V, J sc of 22.64 mA cmâ€"2 and fill factor of 0.70. This systematic work provides an approach to improving V oc and establishes a guideline for developing A-DA′D-A type acceptors with thiophene- or thieno[3,2- b ]thiophene-containing end group. [ABSTRACT FROM AUTHOR]

Tin sulfide (SnS) semiconductor has recently attracted a great deal of attention from the scientific community regarding its application in solar cells. However, SnS solar cell efficiencies are still limited to less than 5%. The incorporation of nanostructures into solar cells has been demonstrated to be a potential route to improve device performance. So far, there have been no reports on the incorporation of nanostructures into SnS solar cells. In this work, a theoretical study on the incorporation of tin sulfide selenide (SnSSe) nanostructures in the form of quantum wells (QWs) into SnS solar cells under the radiative limit is presented, for the first time. In particular, the impact of well number, well thickness, and Se/(S + Se) compositional ratio at the wells, on solar cell characteristics, is evaluated. An efficiency enhancement of 11.1% is found for a SnS/SnSSe QW solar cell, compared to the optimized device without nanostructures, for 50 wells of 54 nm width with a Se/(S + Se) well composition of 0.4 and considering barrier thicknesses of 5 nm, which is a result of the increase in short-circuit current density of 14.5%. The influence of defects at wells and barriers, as well as defects at interfaces, on solar cell behavior is also presented, demonstrating that the introduction of QWs can result in higher efficiencies than that of the device without nanostructures. In this sense, the addition of SnSSe nanostructures to SnS solar cells is introduced as a potential route to promote the absorption of photons with energy lower than the SnS band-gap, while keeping open-circuit voltage values similar to those of a SnS solar cell without nanostructures, thereby increasing solar cell efficiency. [ABSTRACT FROM AUTHOR]

In this letter, the role of domain wall (DW) on bulk photovoltaic effect (BPV) effect in BiFeO3 (BFO) films was studied by x-ray reciprocal space mapping and conductive atomic force microscope. It was found that the domain structure and DW can be tuned by controlling the epitaxial orientation of BFO film. Remarkably, under 1 sun AM 1.5 G illumination, the 109° DW enhances the transport of photogenerated carriers and simultaneously improves the conductivity and power conversion efficiency (PCE). The short-circuit current density and PCE can reach 171.15 μA cm−2 and 0.1127%, respectively. Therefore, our study reveals the correlation between the DW and the BPV effect in BFO film and provides a new pathway to improve the PCE of BFO-based photovoltaic device. [ABSTRACT FROM AUTHOR]

Atomic-force microscopic images, x-ray diffraction patterns, Urbach energies and photoluminescence quenching experiments show that the interfacial contact quality between the hydrophobic [6,6]-phenyl-C61-buttric acid methyl ester (PCBM) thin film and hydrophilic CH3NH3PbI3 (MAPbI3) thin film can be effectively improved by using a binary antisolvent mixture (toluene:dichloromethane or chlorobenzene:dichloromethane) in the anti-solvent mixture-mediated nucleation process, which increases the averaged power conversion efficiency of the resultant PEDOT:PSS (P3CT-Na) thin film based MAPbI3 solar cells from 13.18% (18.52%) to 13.80% (19.55%). Beside, the use of 10% dichloromethane (DCM) in the binary antisolvent mixture results in a nano-textured MAPbI3 thin film with multicrystalline micrometer-sized grains and thereby increasing the short-circuit current density and fill factor (FF) of the resultant solar cells. It is noted that a remarkable FF of 80.33% is achieved, which can be used to explain the stable photovoltaic performance without additional encapsulations. [ABSTRACT FROM AUTHOR]

Multiterminal high voltage direct current (HVDC) systems are developing rapidly lately. However, the high rising rate of fault current and the lack of interrupting capacity of the available DC circuit breakers hinder the further development of multiterminal HVDC systems. Being aimed at the challenge, this paper proposes a novel inductive DC superconducting fault current limiter (SFCL) to cooperate with available DC circuit breakers to cope with the short-circuit fault current in a multiterminal HVDC system effectively. In the normal power transmission of a multiterminal HVDC system, the SFCL presents low impedance and enables a smooth reclosing operation after an interruption. It is able to make a maximum use of the permeability of the iron core to offer a large inductance to curb the rising rate of the fault current in the early few milliseconds as a fault takes place. In addition, it can have an adjustable current limiting threshold to match the different requirements of different grid protection schemes. In this paper, first the working principle of the proposed SFCL is introduced. Then the experimental results on a concept-proofing prototype are reported and analyzed. The experimental results have verified the principle and functional ability of the proposed SFCL. [ABSTRACT FROM AUTHOR]

To evaluate the performance of GaNAsBi alloys as solar cell materials, a GaNAsBi double-heterostructure pin solar cell was fabricated using plasma-assisted solid source molecular beam epitaxy. The addition of even a small amount of N (less than 1%) to the GaAsBi alloy significantly reduces the short-circuit current density (Jsc) of the solar cell. However, after thermal annealing, Jsc increases by ∼6.5 times. After thermal annealing, the GaN0.006As0.966Bi0.028 solar cells (bandgap (Eg) = 1.15 eV) exhibited an open-circuit voltage (Voc) of 0.35 V, Jsc of 10.2 mA cm−2, and fill factor of 0.56. Based on the Urbach energy of Ga(N)AsBi, the decreased crystallinity associated with the addition of N leads to poor characteristics of GaNAsBi solar cells compared with those GaAsBi solar cells. [ABSTRACT FROM AUTHOR]

The high-Tc superconducting (HTS) dynamo exploits the nonlinear resistivity of an HTS tape to generate a DC voltage when subjected to a varying magnetic field. This leads to the so-called flux pumping phenomenon and enables the injection of DC current into a superconducting coil connected to the dynamo without current leads. In this work, the process of charging a coil by an HTS dynamo is examined in detail using two numerical models: the minimum electromagnetic entropy production and the segregated -formulation finite element model. The numerical results are compared with an analytical method for various airgaps and frequencies. Firstly, the I–V curves of the modeled HTS dynamo are calculated to obtain the open-circuit voltage, short-circuit current and internal resistance. Afterward, the process of charging a coil by the dynamo including the charging current curve and its dynamic behavior are investigated. The results obtained by the two models show excellent quantitative and qualitative agreement with each other and with the analytical method. Although the general charging process of the coil can be obtained from the I–V curve of the flux pump, the current ripples within a cycle of dynamo rotation, which can cause ripple AC loss in the HTS dynamo, can only be captured via the presented models. [ABSTRACT FROM AUTHOR]

In this article, the synthesis of phase pure iron pyrite nanocubes (FeS2 NCs) and their various effects on the charge carrier dynamics and photovoltaic performances of P3HT:PC71BM based hybrid bulk-heterojunction solar cells have been studied. The optimum doping concentration of FeS2 NCs was found to be 0.3 wt%. For the optimally doped devices, the short-circuit current density was found to have improved from 5.47 to 7.99 mA cm−2 leading to an overall cell efficiency improvement from 2.10% to 3.22% as compared to the undoped reference devices. The enhancement in photovoltaic performance is mainly attributed to the formation of localized energy states near the band edges leading to higher carrier generation rate by 72% whereas carrier dissociation probability is also increased by 13%. Urbach energy estimation reveals that the optimally doped devices have achieved a relatively balanced amount of localized states resulting in reduced non-radiative recombination. Such localized defect states formation with FeS2 NCs doping was also found to have significant influence over the charge carrier dynamics of the active layer. Transient photocurrent and photovoltage studies revealed that FeS2 NCs assist in faster carrier extraction by reducing the transport time from 1.4 to 0.6 μs and by enhancing carrier recombination time from 51.7 to 78.9 μs for the reference and optimum devices respectively. Such an unorthodox approach of defect state assisted efficiency improvement demonstrates the importance of simultaneously understanding the charge carrier dynamics and photovoltaic performance for rational device optimization, and opens new prospects for developing high-efficiency solution processable hybrid devices. [ABSTRACT FROM AUTHOR]

Medium voltage load break switches (MV-LBS) should pass fault current while closing and be able to re-open for the next operation. Replacing SF6 as a high impact greenhouse insulating gas with air, makes the switch design more challenging because of the higher pre-strike arcing time and energy dissipation between contacts which leads to more contact surface erosion and an even higher possibility of welding. In this paper, a synthetic test circuit is used to emulate stresses applied to MV-LBS during the making of short-circuit currents. Since there are difficulties in accurate direct measurement of arc voltage because of the inherent response of the measurement system, an alternative method using optical emission spectroscopy (OES) is proposed. OES measures the pre-strike arc temperature distribution profile close to the cathode surface at a test voltage of 18 kV and a making current of 17 kA. The arc electrical characterization is achieved using the obtained spectroscopy results, Lowke's model and thermal air plasma transport properties. A maximum arc temperature of 12 500 K while the arc moves from the lower part of the cathode to the center, arc voltage of 30–58 V, and dissipated energy of 79–87 J are calculated for the pre-strike arc considering the impact of copper evaporated from the contact surfaces. Different arc behavior is observed in closing the contacts compared to free-burning arcs, which indicates gas flow blowing the arc caused by the contact movement. This investigation could be used for a better understanding of switching behavior and efficient control of the operation. [ABSTRACT FROM AUTHOR]

The tandem structure is promising to break the Shockley–Queisser limit of single-junction solar cells. Optical management is essential in two-terminal (2T) tandem devices to equalize the current of each sub-cell and enhance the performance. In this work, the photon redistribution effect caused by the optical coupling layer (OCL) and its impact on 2T perovskite/Si tandem solar cells are systematically investigated. We modulate the overall optical field distribution to balance the current of the two sub-cells by structural modulation. The introduction of an OCL affects the photon distribution in the 2T tandem device, which disturbs the original current match and complicates the optical management. In addition to the antireflection function, the photon redistribution effect due to the coupling effects exists for each type of OCL. Various materials (LiF, MgF2, Al2O3 and ZnO) are employed as OCLs and compared. It is shown that they influence the device performance to different degrees. Compared to LiF and MgF2, the influence of the 2T tandem device on short-circuit current density is more significant when Al2O3 and ZnO act as OCLs. By investigating the optical mechanism and then improving the optical management, an optimized device performance can be achieved. We believe that it is necessary to consider the coupling effect in the structural design of 2T tandem solar cells. [ABSTRACT FROM AUTHOR]

The electronic and ionic conductivities of the interphase that forms between Li metal and solid electrolytes (SEs) are key parameters in determining battery cell performance. In this study, we evaluated the effect of the interphase on Li dissolution/deposition behaviors. The reduction of Li2S-P2S5 glasses to Li2S and Li3P by Li metal occurred at the Li/SE interface. The Li dissolution/deposition performance at 100 °C was improved by increasing the Li3P content in the interphase, and the cell with a Li4P2S6 glass electrolyte functioned without short-circuiting at a current density of 1.3 mA cm-2. The ionic conductivity of the Li/SE interphase was evaluated by preparing Li-SE compounds using mechanochemical processing. The milled sample prepared from Li metal and Li4P2S6 glass showed a one order of magnitude higher conductivity of 10-4 S cm-1 at 100 °C than that of the Li-Li3PS4 milled sample, indicating that the ionic conductivity of the interphase formed at the Li/SE interface is an important factor for improving the short-circuiting tolerance of all-solid-state Li-metal batteries. [ABSTRACT FROM AUTHOR]

The synthesis of Ag2S quantum dots (QDs) deposited on the surface of electrodeposited ZnO nanorods (NRs) by a successive ionic-layer adsorption and reaction (SILAR) method is reported. A Box-Behnken response surface factorial design was used to organize the experiments conducted and identify the effects of three electrochemical parameters and their potential interactions. These parameters include zinc precursor concentration in the electrolytic bath, the electrolytic bath temperature and the electrodeposition time on the morphological and structural properties of the electrochemically grown ZnO nanorods. Morphological, structural and optical characterizations of these NRs heterojunctions were done. A direct band gap for Ag2S QDs, tuned between 2.54 and 2.73 eV by varying the SILAR cycle numbers, was determined. The presence of ZnO nanostructures increases the light scattering capability of the samples, allowing an important quantity of diffuse light near the absorption edge of Ag2S. The photoelectrochemical performance of these ZnO NRs decorated with Ag2S QDs based photoanodes has been evaluated. The SILAR parameters related to the growth of the Ag2S QDs that optimize the performance of this photoelectrode are presented. The effect of a ZnS passivation layer has been studied leading to an increase of about 400% in the short-circuit current density after passivation. [ABSTRACT FROM AUTHOR]

In this work, a type-III heterojunction based on a pulsed-laser-deposited vanadium dioxide (VO2) and p-type silicon (p-Si) substrate is realized. The device shows a large self-powered and room-temperature photoresponse to IR (950 nm), green (515 nm) and blue (456 nm) LEDs. A short-circuit current (Isc) of ∼3 µA and an open-circuit voltage (Voc) of ∼−120 mV are observed under IR LED illumination. The work function data in literature along with the sign of Voc measurement is used to sketch the energy band diagram of the heterojunction. The temperature-dependent Isc properties of the junction, contrary to conventional photodetectors, show an initial rise and then a sharp transition from maximum (3.5 μA) to almost zero near 337 K, corresponding to a metal–insulator phase transition, paving the way for photodetectors with temperature-tunable photoresponsivity. [ABSTRACT FROM AUTHOR]

Inorganic perovskite CsPbBr3 is a material used for fabricating highly efficient and stable perovskite solar cells. In this work, a two-step infiltration-spinning method is proposed to obtain CsPbBr3 films with pure phase. Phase transformations between CsPb2Br5, CsPbBr3 and Cs4PbBr6 are investigated by controlling the contact time between the CsBr solution and the PbBr2 substrate. CsPbBr3 films with large grain sizes are obtained after high temperature post-treatment. The CsPbBr3-based solar cells show a high efficiency (approximately 7%) with a short-circuit current density of 6.68 mA cm−2, an open-circuit voltage of 1.47 V and a fill factor of 70.9% under standard solar illumination. [ABSTRACT FROM AUTHOR]

In this study, two different n-CdS/p-Cu2S solar cells were prepared by evaporating Cu at different substrate temperatures (200 K and 300 K) by vacuum evaporation method on a single crystal CdS semiconductor. Field emission scanning electron microscope images showed that the Cu layer obtained at a temperature of 200 K was composed of nanoparticles in accordance with the soliton growth mechanism. Cu film thickness was determined as 395 ∓ 0.76 nm at 300 K substrate temperature and 187 ∓ 0.45 nm at 200 K substrate temperature. The current–voltage (I–V) and capacitance–voltage (C–V) characteristics of the solar cells were examined for 12 weeks in dark and light environments. Open-circuit voltage (Voc), short-circuit current (Isc), maximum power (Pmax), filling factor and efficiency (η) were calculated from I–V measurements. For the prepared solar cells, the highest efficiency value was obtained in the 7th week (η= 0.1360) at 200 K substrate temperature, while it was obtained in the 5th week (η = 0.0384) at 300 K substrate temperature. From C–V measurements, donor density (Nd) and barrier potential (Vbi) were calculated. The solar cell produced at 200 K substrate temperature has higher donor density (1st week 2.99 × 1016 cm−3) and barrier potential values (12th week 0.411 V). At the end of the 12-week period, the deterioration rate of solar cells created at 200 K and 300 K substrate temperatures was 51% and 94%, respectively. [ABSTRACT FROM AUTHOR]

The broadband absorption enhancement effect in ultrathin molybdenum disulfide (MoS2) films is investigated. It is achieved by inserting the MoS2 film between a dielectric film and a one-dimensional silver grating backed with a silver mirror. The broadband absorption enhancement in the visible region is achieved, which exhibits large integrated absorption and short-circuit current density for solar energy under normal incidence. The optical properties of the proposed absorber are found to be superior to those of a reference planar structure, which makes the proposed structure advantageous for practical photovoltaic application. Moreover, the integrated absorption and short-circuit current density can be maintained high for a wide range of incident angles. A qualitative understanding of such broadband absorption enhancement effect is examined by illustrating the electromagnetic field distribution at some selected wavelengths. The results pave the way for developing high-performance optoelectronic devices, such as solar cells, photodetectors, and modulators. [ABSTRACT FROM AUTHOR]

The practical implementation of air-breathing microbial fuel cell (MFC) is critically linked to the development of efficient materials as cathode and electrochemically active biofilm-based anode. In this contribution, we demonstrate the feasibility by decorating a 3D carbon felt electrode with Pt nanoarrays (CF@Pt) as a bifunctional electrode material as efficient garden compost bioanode and airbreathing cathode. Half-cell electrochemical characterizations reveal that the onset potential of the anode reaction negatively shifts of about 800 mV to reach -0.4 V vs Ag/AgCl after the growth of the biofilm onto CF@Pt. The investigation before and after the biofilm formation shows that Pt nanoarrays act as excellent electron relays, reducing significantly the charge transfer resistance. For MFC application (with a proton exchange membrane), the use of CF@Pt as bioanode' scaffold and CF@Pt air-cathode enables a drastically enhanced power density of Pmax = 292.3 mWm-2, and a high short-circuit current density jsc = 1.9 A m-2. [ABSTRACT FROM AUTHOR]

In this study, highly-aligned and molecularly oriented poly(vinylidene fluoride/trifluoroethylene) [P(VDF/TrFE)] nanofiber webs were fabricated and their piezoelectric response was investigated. Using systematic post-treatments under appropriate conditions, a significant enhancement of the piezoelectric response in the P(VDF/TrFE) nanofiber webs was observed for the first time. The high-quality nanofibers exhibited a large output voltage of 0.4 V. The short-circuit current of post-treated nanofibers was found to be 731.25 μA, which increased about 330 times and the surface electric charge density was found to be 0.64 nC cm−2, which was about 2.7 times higher than those of the as-spun nanofibers. The large enhancement of piezoelectric response of the nanofibers is attributed to the additional stretching, annealing and poling of the as-spun nanofibers under the appropriate post-treatment conditions. The results highlight the potential of the high-quality P(VDF/TrFE) nanofibers to be used as wearable piezoelectric energy harvesters and other flexible self-powered portable devices. [ABSTRACT FROM AUTHOR]

This study demonstrates the performance improvement of ultrasonic spray deposited bulk heterojunction type polymer solar cells through droplet boundary reduction assisted by acoustic substrate vibration of varying frequencies between 0–20 kHz. The optimum performance was achieved at 15 kHz of applied frequency, where ∼68% improvement in short-circuit current density and ∼85% improvement in overall cell efficiency were observed compared to the reference devices fabricated on stationary substrates. The performance enhancement is mainly attributed to the improved film morphology due to uniform and homogenous droplet spreading and coalescence under the influence of acoustic vibration. Systematic improvement was observed until 15 kHz when smooth films with significantly reduced droplet boundaries were observed with surface roughness around 10 nm only. However, beyond this point, higher frequencies were found to have detrimental effect on film formation. Significant improvement was observed for every cell parameter for 15 kHz samples. Almost ∼16% enhancement in carrier generation rate and ∼46% enhancement in exciton dissociation probability were observed, as estimated from the photo-current analysis. Urbach energy estimation reveals that the films, prepared at 15 kHz substrate vibration, forms less amount of band edge localized defect states (Eu(no vibration) = 161 meV and Eu(15 kHz) = 120 meV), resulting into reduced non-radiative recombination and better performances. The presented approach opens up new pathways for uniform and scalable thin film growth through acoustic substrate vibration assisted ultrasonic spray deposition technique, which would be beneficial for large scale industrial organic photovoltaic production. [ABSTRACT FROM AUTHOR]

In this paper, coupled optical and electrical simulations of perovskite solar cells (PSCs) are performed to optimize their basis output parameters and obtain the best power conversion efficiency (PCE) based on both the light absorption and carrier transport mechanisms. Due to the limitations of perovskite absorption in longer wavelengths, we used an extra photo-active material of GeSe with a narrower bandgap and a broader absorbing spectrum to increase the efficiency of the PSC. To prevent carrier transmission disorder that exists in the planar structure with two absorbing materials, GeSe was inserted into the main active layer in the form of nanowires (NWs). As a result, it improved the carrier transfer and open-circuit voltage (Voc) in addition to the short-circuit current density (Jsc). The behavior of PSC with different sizes of GeSe NWs at the same density was investigated to determine the appropriate size of NWs and achieve the highest PCE. In the optimal structure with 50 nm diameter NWs, Jsc and PCE of the cell are 22.96 mA cm−2 and 18.97%, which are improvements of 39% and 50%, respectively, compared to the planar structure studied at the beginning of the paper. [ABSTRACT FROM AUTHOR]

The time effect of tritium silicon p–n junction betavoltaic batteries is considered in this work. For a titanium tritium (TiT2) source, the processes of decaying, tritium leaking, swelling and 3He releasing are contained in the calculation, and expressions of component and density changes are obtained. As time goes by, the self-absorption rate has a downward trend, while all electrical performances decrease, especially the short-circuit current (ISC) and the maximum output power (Pmax). At about 3.5 a, the battery begins to release gaseous 3He, and the expiry date of the battery is about 10.7 a, shorter than the half-life of tritium. The result indicated that for a tritium source, the time leads to a significant reduction in the electrical performance of the battery, which cannot be ignored in simulations and experiments. [ABSTRACT FROM AUTHOR]

The time effect of tritium silicon p–n junction betavoltaic batteries is considered in this work. For a titanium tritium (TiT2) source, the processes of decaying, tritium leaking, swelling and 3He releasing are contained in the calculation, and expressions of component and density changes are obtained. As time goes by, the self-absorption rate has a downward trend, while all electrical performances decrease, especially the short-circuit current (ISC) and the maximum output power (Pmax). At about 3.5 a, the battery begins to release gaseous 3He, and the expiry date of the battery is about 10.7 a, shorter than the half-life of tritium. The result indicated that for a tritium source, the time leads to a significant reduction in the electrical performance of the battery, which cannot be ignored in simulations and experiments. [ABSTRACT FROM AUTHOR]

In this work, a path to overcome the highest current efficiency on SnS thin-film solar cells by the Se incorporation is presented. We carried out a theoretical study of the effect of different Se/(S + Se) compositional ratios (CRs) (from 0.0 to 1.0) on the solar cell performance. In this sense, an improvement on power conversion efficiency (PCE) by decreasing the energy band gap (theoretical Se incorporation) from 1.35 to 1.08 eV was observed. All electrical output parameters (open-circuit voltage, short-circuit current density, fill factor and PCE) were increased by an augment of the CR from 0.25 to 0.75. A PCE of 10.23% was obtained for a CR of 0.75. Furthermore, a thickness optimization of the absorber was carried out, where the greatest PCE of 11.78% was obtained at 800 nm. On the other hand, a simulation at different work functions in back contact and different bulk defect density on the absorber were performed in order to achieve higher efficiencies. [ABSTRACT FROM AUTHOR]

Wurtzite-structured CdS material is widely used in information sensing and energy harvesting. Based on the piezoelectric property of CdS, we present a flexible piezoelectric nanogenerator (PENG) with three-dimensional-structured CdS nanowall arrays. Under index finger oscillations at a slow rate, the maximal open-circuit voltage and short-circuit current are 1.2 V and 6 nA respectively. Meanwhile, the working mechanism of this PENG was successfully studied with piezoelectric potential distribution and energy band theory respectively. All of the results show that an increase in the bending degree and bending frequency will affect the output of the PENG, suggesting that it can be used as a flexible sensor. In addition, the fabricated PENG can be used as a self-powered pressure sensor relying on the linear relationship between the output voltage and the vertical pressure. This work may provide a new approach to fabricating piezoelectric nanogenerators based on three-dimensional materials as an energy harvester, which may also facilitate the development of flexible and wearable electric sensing technology. [ABSTRACT FROM AUTHOR]

SiO2 nanoparticles were used to regulate the crystallizing process of lead halide perovskite films prepared by the sequential deposition method, which was used in the low-temperature-processed, carbon-electrode-basing, hole-conductor-free planar perovskite solar cells. It was observed that, after adding small amount of SiO2 precursor (1 vol%) into the lead iodide solution, performance parameters of open-circuit voltage, short-circuit current and fill factor were all upgraded, which helped to increase the power conversion efficiency (reverse scan) from 11.44(± 1.83)% (optimized at 12.42%) to 14.01(±2.14)% (optimized at 15.28%, AM 1.5G, 100 mW/cm2). Transient photocurrent decay curve measurements showed that, after the incorporation of SiO2 nanoparticles, charge extraction was accelerated, while transient photovoltage decay and dark current curve tests both showed that recombination was retarded. The improvement is due to the improved crystallinity of the perovskite film. X-ray diffraction and scanning electron microscopy studies observed that, with incorporation of amorphous SiO2 nanoparticles, smaller crystallites were obtained in lead iodide films, while larger crystallites were achieved in the final perovskite film. This study implies that amorphous SiO2 nanoparticles could regulate the coarsening process of the perovskite film, which provides an effective method in obtaining high quality perovskite film. [ABSTRACT FROM AUTHOR]

Recently, significant progress in the field of organic photovoltaic cells was obtained by substituting new electron acceptor molecules to the fullerene, which was attributed to the fact that the fullerene absorption is quite small. Nevertheless, we demonstrate in the present work that, in the case of inverted cells, i.e. when the transparent bottom electrode is used as cathode, the contribution of fullerene to the Jsc short-circuit current of the cells, if not dominant, is not negligible; and that mainly in the short wavelength spectral range. The experimental results are confirmed by an optical simulation. Due to this significant contribution to Jsc, the light transmission of the transparent electrode towards the UV-part of the spectrum is crucial for inverse cell performances. When a transparent conductive electrode based on an alternative dielectric/metal/dielectric structure is substituted to ITO, such as ZnS/Ag/TiO2, the study allows to obtain promising results, although there is a loss of performance due to the decrease of transmission of TiO2 below 400 nm in wavelength. [ABSTRACT FROM AUTHOR]

Resistive-type superconducting fault current limiters (R-SFCLs) can limit short-circuit fault current and help DC circuit breakers (DCCBs) to isolate short-circuit faults in medium voltage and high voltage DC (HVDC) systems. SFCLs are always used with circuit breakers to break short-circuit current in power systems. The interruption characteristics of the DCCBs influence the current-limiting characteristics of the SFCLs. However, there has been a lack of investigation into the current-limiting and interruption characteristics when R-SFCLs are combined with mechanical-type DCCBs (M-DCCBs) based on the self-excited oscillation interruption principle in medium voltage and HVDC systems. The objective of this paper is to obtain the short-circuit fault current-limiting characteristics of a designed R-SFCL combined with an M-DCCB in DC grids. This paper describes the design of a 10 kV DC R-SFCL which was tested in combination with an M-DCCB in a DC circuit in order to obtain the quenched resistance and the required current interruption characteristics. Besides, a modular multilevel converter-based multi-terminal direct current (MMC-MTDC) grid was used to investigate the current-limiting and interrupting characteristics of the R-SFCL and the M-DCCB in a realistic HVDC grid. The experimental results show that in the 10 kV DC circuit the R-SFCL combined with the M-DCCB limited a 10 kA DC to the peak value of 1416 A and then interrupted this limited current successfully. And unlike other methods of DC interruption, this did not create overvoltage after interruption. The highest voltage on the R-SFCL is the system voltage during interruption. This means that the R-SFCL can effectively delay the voltage drop in MMC-MTDC grids, and provide enough time for the M-DCCB to interrupt the limited current. Thus, a combination of R-SFCLs and M-DCCBs might be an effective and reliable method to interrupt short-circuit fault currents in medium voltage and HVDC grids. [ABSTRACT FROM AUTHOR]

We demonstrate that the optical absorption is enhanced in small molecule organic solar cells by using a trapezoid grating structure. The enhanced absorption is mainly attributed to both waveguide modes and surface plasmon modes, which is simulated by using finite-difference time-domain method. The simulated results show that the surface plasmon along the semitransparent metallic Ag anode is excited by introducing the periodical trapezoid gratings, which induce the increase of high intensity field in the donor layer. Meanwhile, the waveguide modes result in a high intensity field in acceptor layer. The increase of field improves the absorption of organic solar cells significantly, which is demonstrated by simulating the electrical properties. The simulated results also show that the short-circuit current is increased by 31% in an optimized device, which is supported by the experimental measurement. Experimental result shows that the power conversion efficiency of the grating sample is increased by 7.7%. [ABSTRACT FROM AUTHOR]

The performance of a multiple quantum well (MQW) InGaN solar cell with double indium content is investigated. It is found that the adoption of a double indium structure can effectively broaden the spectral response of the external quantum efficiencies and optimize the overall performance of the solar cell. Under AM1.5G illumination, the short-circuit current density (Jsc) and conversion efficiency of the solar cell are enhanced by 65% and 13% compared with those of a normal single-indium-content MQW solar cell. These improvements are mainly attributed to the expansion of the absorption spectrum and better extraction efficiency of the photon-generated carriers induced by higher polarization. [ABSTRACT FROM AUTHOR]

Single-junction, lattice-mismatched In0.69Ga0.31As thermophotovoltaic (TPV) devices each with a bandgap of 0.6 eV are grown on InP substrate by metal-organic chemical vapour deposition (MOCVD). Compositionally undulating stepgraded InAsyP1-y buffer layers with a lattice mismatch of ∼1.2% are used to mitigate the effect of lattice mismatch between the device layers and the InP substrate. With an optimized buffer thickness, the In0.69Ga0.31As active layers grown on the buffer display a high crystal quality with no measurable tetragonal distortion. High-performance single-junction devices are demonstrated, with an open-circuit voltage of 0.215 V and a photovoltaic conversion efficiency of 6.9% at a short-circuit current density of 47.6 mA/cm², which are measured under the standard solar simulator of air mass 1.5-global (AM 1.5 G). [ABSTRACT FROM AUTHOR]

A short-circuited lithium-ion battery cell is likely to generate sufficient heat to initiate exothermic side reactions causing thermal runaway. A 2D coupled electrochemical-thermal model was developed to investigate a prismatic LiNi0.8Co0.15Al0.05O2∣LiPF6, EC/EMC (3:7)∣MAG-10 battery cell that is short-circuited. Three short-circuit scenarios are investigated during the events from when short circuit occurs until exothermic side reactions initiate. The scenarios are an external short circuit, a nail penetration and an impurity-induced short circuit. The model is used to predict the temperature increase within the cell and to explain how the interrelation between the electrochemical processes and the thermal properties affects the increase. Important safety measures are also examined with the model. The simulation results highlight general short-circuit characteristics and critical distinctions between the scenarios. The mass transport of lithium ions in the electrolyte is found to be the most important general characteristic that determines the rate of the temperature increase. The electric resistance distinguishes the scenarios from each other. The rate of the temperature increase is dictated by the mass transport in the electrolyte even when large variations in available active material are made and it is shown to be difficult to slow down the rate by cooling. [ABSTRACT FROM AUTHOR]

Upconversion of sunlight with energy below the band gap of a solar cell is a promising technique for enhancing the cell efficiency, simply by utilizing a larger part of the solar spectrum. The present topical review addresses this concept and discusses the material properties needed for an efficient upconversion process with focus on both silicon and organic solar cells. To design efficient upconverters, insight into topics such as quantum-optics, nano-optics, numerical modeling, optimization, material fabrication, and material characterization is paramount, and the necessary concepts are introduced throughout the review. Upconversion modeling is done using rate equations, while optical modeling is done by solving Maxwell’s equations using the finite element method. Topology optimization is introduced and used to generate geometries of gold nanoparticles capable of greatly enhancing the upconversion yield. Fabrication and experimental characterization methods are discussed. Some recent results are presented and finally the possibility of designing upconverting materials capable of increasing the short-circuit current in a solar cell is discussed. [ABSTRACT FROM AUTHOR]

The spectral responsivity of solar cells is widely used for cell analysis or calibration purposes. According to the IEC60904-8:2014 standard, the reference method for the determination of is the complete differential spectral responsivity approach. For this approach, the differential spectral responsivity is measured as a function of wavelength and bias irradiance. To obtain the spectral responsivity related to standard test conditions the IEC60904-8:2014 standard recommends to integrate via bias current for each wavelength. We show that this integration is wrong. It lacks analytical derivation and provides faulty curves for non-linear solar cells. We prove analytically and by means of simulations that the correct way of calculation is either the integration of via the bias irradiance or the integration of via the bias current , with being the AMx-weighted (e.g. AM1.5G or AM1.5D) differential responsivity. A simulation of the differential spectral responsivity of a strongly non-linear solar cell demonstrates deviations of up to 30% for (the wrong) integration of via at some wavelengths, corresponding to a deviation in the short-circuit current of up to 3.0%. [ABSTRACT FROM AUTHOR]

In order to obtain higher conversion efficiency and to reduce production cost for hydrogenated amorphous silicon/crystalline silicon (a-Si:H/c-Si) based heterojunction solar cells, an a-Si:H/c-Si heterojunction with localized p–n structure (HACL) is designed. A numerical simulation is performed with the ATLAS program. The effect of the a-Si:H layer on the performance of the HIT (heterojunction with intrinsic thin film) solar cell is investigated. The performance improvement mechanism for the HACL cell is explored. The potential performance of the HACL solar cell is compared with those of the HIT and HACD (heterojunction of amorphous silicon and crystalline silicon with diffused junction) solar cells. The simulated results indicate that the a-Si:H layer can bring about much absorption loss. The conversion efficiency and the short-circuit current density of the HACL cell can reach 28.18% and 43.06 mA/cm2, respectively, and are higher than those of the HIT and HACD solar cells. The great improvement are attributed to (1) decrease of optical absorption loss of a-Si:H and (2) decrease of photocarrier recombination for the HACL cell. The double-side local junction is very suitable for the bifacial solar cells. For an HACL cell with n-type or p-type c-Si base, all n-type or p-type c-Si passivating layers are feasible for convenience of the double-side diffusion process. Moreover, the HACL structure can reduce the consumption of rare materials since the transparent conductive oxide (TCO) can be free in this structure. It is concluded that the HACL solar cell is a promising structure for high efficiency and low cost. [ABSTRACT FROM AUTHOR]

CdTe is one of the leading materials for low cost, high efficiency thin-film solar cells with a nearly ideal band gap of 1.48 eV. However, its solar to electricity power conversion efficiency (PCE) is hindered by the relatively low open circuit voltage (VOC) due to intrinsic defect related issues. Here, we propose that alloying CdTe with CdSe could possibly improve the solar cell performance by reducing the “ideal” band gap of CdTe to gain more short-circuit current from long-wavelength absorption without sacrificing much VOC. Using the hybrid functional calculation, we find that the minimum band gap of the CdTe1−xSex alloy can be reduced from 1.48 eV at x = 0 to 1.39 eV at , and most of the change come from the lowering of the conduction band minimum. We also show that the formation of the alloy can improve the p-type doping of CuCd impurity based on the reduced effective formation energy and nearly constant effective transition energy level, thus possibly enhance VOC, thus PCE. [ABSTRACT FROM AUTHOR]

Pursuits of wearable electronics include the features of flexible, self-powered, and even being ultrathin and transparent for a better fit on different curved surfaces in an imperceptible way. In this paper, by stacking two graphene-covered parylene films layer by layer and introducing serpentine structures in one parylene film as the spacer, ultraflexible triboelectric nanogenerators (TENGs) with a total thickness of 5.5 μm and a transmittance of 80% were achieved. Under the stimulation of vertical impacts at frequencies of 0.5 Hz, 1 Hz, 1.5 Hz, 2 Hz, and 2.5 Hz, an open-circuit (OC) voltage of 3 V was maintained in a TENG measuring 2  ×  2 cm2 throughout all the cases, which indicated a good mechanical stability of the device. When the TENG was bent, there was an increase in OC voltage and short-circuit current in response to an increased curvature. Due to its ultrathin nature and being sensitive to curvature, the TENG was demonstrated to serve as a self-powered curvature sensor for movement monitoring when conformably attached on the finger joint. [ABSTRACT FROM AUTHOR]

In this study, a recorded high open-circuit voltage (Voc) of 1.61 V and fill factor (FF) of 76.65% of a-Si:H p-i-n/heterojunction with intrinsic thin layer (HIT)-type multi-junction solar cells were achieved using grain size enlargement within the p-type μc-Si:H layer in a p-type μc-Si:H/n-type a-Si:H tunneling recombination junction (TRJ) layer. The p-type μc-Si:H layer’s conductivity increased from 1.74 × 10−4 to 0.1 S cm−1 as the film’s crystallinity increased from 41.5% to 67.5%. The a-Si:H p-i-n/HIT-type multi-junction solar cells also benefited from the tuning up crystalline p-type μc-Si:H layer, showing the increase of Voc and FF from 1.5 V and 49.88% to 1.61 V and 76.65%, respectively; while the short-circuit current density (9.38 ± 0.2 mA cm−2) did not change significantly. These are the highest Voc and FF values achieved in a-Si:H p-i-n/HIT-type multi-junction solar cells, recently. From dark current-voltage analysis, it was deduced that the enhanced crystalline films could assist in suppressing carrier interference in the TRJ layer, thus reduces electric field distortion and mitigates recombination in the device. In summary, an enhanced crystalline p-type μc-Si:H layer could be a viable option for ensuring an excellent TRJ layer, thus achieved high efficiency of inorganic/c-Si tandem solar cells. Using optimal condition with crystallinity of 74.1%, the photovoltaic parameters of the device yield Voc, Jsc and FF of 1.51 V, 13.01 mA cm−2 and 71.45%, which in turned giving an efficiency of 14.04% for a-SiGe:H p-i-n/HIT-type tandem solar cell. [ABSTRACT FROM AUTHOR]

The short-circuit current output of photovoltaic (PV) reference device is typically used to determine the incident irradiance of natural or simulated sunlight. Normally the PV reference device is calibrated at standard test conditions and other irradiances are calculated based on a proportionality assumption (termed linearity) between short-circuit current output and incident irradiance. Here the linearity of PV devices is newly defined including a quantitative correction for non-linearity (NL) when measuring incident irradiance. Linearity can be determined experimentally by the flux addition principle such as in the two-lamp method. The latter provides information about linearity between two irradiance levels which differ by a factor of two, but no information on linearity inside this interval. Here this concept is extended to the N-lamp method. It is shown that this provides more detailed linearity information with low uncertainty. Measurements were made with an 11-lamp steady-state solar simulator and showed a NL deviation of 2% in the irradiance range from 100 W m−2 to 1100 W m−2 for the PV reference cell tested. The method is easily implemented, provides detailed quantitative linearity assessment at low cost and can be considered a primary method for linearity assessment, as it does not require any reference device. [ABSTRACT FROM AUTHOR]

GaInNAs with bandgap 1.0 eV is a promising material for multi-junction solar cell applications. However, the poor quality of GaInNAs grown by metalorganic chemical vapor deposition hinders its device performance. Here to reap the benefits of 1.0-eV sub-cell, we focus on the optimization of annealing temperature and growth ambient of GaInNAs. The GaInNAs sub-cell exhibits a concentration reduction of shallow level defects when it is annealed at 700 °C for 20 min. As compared with the growth case using a hydrogen ambient, the N incorporation efficiency of GaInNAs can be enhanced during the growth in an N2 ambient. Furthermore, background carbon concentration is observed to reduce in the as-grown GaInNAs epilayer. A GaInNAs sub-cell with 82% peak external quantum efficiency is obtained in a dual-junction GaInNAs/Ge solar cell. Finally, a monolithic AlGaInP/AlGaInAs/GaInAs/GaInNAs/Ge five-junction solar cell is grown for space application. The fabricated device shows a conversion efficiency of 31.09% and a short-circuit current density of 11.81 mA/cm2 under 1 sun AM 0 illumination. [ABSTRACT FROM AUTHOR]

The solar vector is one of the most important parameters for attitude control of nanosatellites. This attitude control must be achieved without the sensors adding significantly to its size or mass. This paper presents a photodiode-based miniature sun sensor, which consists of two triangular pyramidal sensor unit structures, with each unit comprising three micro-silicon photodiodes. The two sensor units are installed on the diagonal of the nanosatellite to form a complete sun sensor capable of achieving a full-field range of solar vector measurements. In this paper, the mathematical model of the short-circuit currents of the silicon photodiodes as a function of the solar vector coordinates is deduced. A sensor sample was built and installed on a nanosatellite model, and the temperature compensation coefficient of the silicon photodiodes was obtained experimentally. The dynamic characteristic, linearity, hysteresis and repeatability of the component were measured. The sun sensor introduced in this paper can be placed on any satellite platform to allow a full range solar vector measurement, and this would result in an increase of only 1.86 g and 0.9 cm3 of the satellite’s mass and volume, respectively. [ABSTRACT FROM AUTHOR]

Three donor materials, namely, tetraphenyldibenzoperiflanthene (DBP), 1,1′-bis (di-4-tolylaminophenyl) cyclohexane (TAPC), tris[4-(5-phenylthiophen-2-yl)phenyl] amine (TPTPA), and C70 based mixed heterojunctions (MHJs), all demonstrate a significantly high short-circuit current (JSC), together with high power conversion efficiency (PCE), even though TAPC and TPTPA are non-absorbing in the visible region. The JSC shows a much larger difference between the C60 MHJs than the C70 MHJs when the same donor is included. The difference between their absorption and photoluminescence spectra is negligible. The 5 wt% DBP blend film shows a more regular morphology, with well-distributed circular grains, than the other two donors. The priority of horizontal orientation is DBP  >  TPTPA  >  TAPC, thus contributing to a higher JSC in DBP MHJ. The DBP MHJ device also demonstrates superior charge collection efficiency, hole mobility, and stability to the TAPC and TPTPA MHJs. [ABSTRACT FROM AUTHOR]

In this paper, a theoretical study of the electrical parameters degradation of different n-type GaAs sub-cells for InGaP/GaAs/Ge triple junction solar cells irradiated with 1 and 5 MeV electrons has been performed by means of computer simulation. Effects of base carrier concentration upon the maximum power point, short-circuit current, open circuit voltage, diffusion current, recombination current and series resistance of these devices have been researched using the displacement damage dose method, the one-dimensional PC1D device modeling program and a home-made numerical code based on genetic algorithms. The radiative recombination lifetime, damage constant for minority-carrier lifetime and carrier removal rate models for GaAs sub-cells have been used in the simulations. An analytical model has been proposed, which is useful to describe the radiation-induced degradation of diffusion current, recombination current and series resistance. Results obtained in this work can be used to predict the radiation resistance of solar cells over a wide range of energies. [ABSTRACT FROM AUTHOR]

InP nanowire arrays with axial p-i-n junctions are promising devices for next-generation photovoltaics, with a demonstrated efficiency of 13.8%. However, the short-circuit current in such arrays does not match their absorption performance. Here, through combined optical and electrical modeling, we study how the absorption of photons and separation of the resulting photogenerated electron–hole pairs define and limit the short-circuit current in the nanowires. We identify how photogenerated minority carriers in the top n segment (i.e. holes) diffuse to the ohmic top contact where they recombine without contributing to the short-circuit current. In our modeling, such contact recombination can lead to a 60% drop in the short-circuit current. To hinder such hole diffusion, we include a gradient doping profile in the n segment to create a front surface barrier. This approach leads to a modest 5% increase in the short-circuit current, limited by Auger recombination with increased doping. A more efficient approach is to switch the n segment to a material with a higher band gap, like GaP. Then, a much smaller number of holes is photogenerated in the n segment, strongly limiting the amount that can diffuse and disappear into the top contact. For a 500 nm long top segment, the GaP approach leads to a 50% higher short-circuit current than with an InP top segment. Such a long top segment could facilitate the fabrication and contacting of nanowire array solar cells. Such design schemes for managing minority carriers could open the door to higher performance in single- and multi-junction nanowire-based solar cells. [ABSTRACT FROM AUTHOR]

Co3O4 samples have been deposited using RF-magnetron sputtering from an oxide target. In situ x-ray and ultraviolet photoelectron spectroscopy and x-ray diffraction have been carried out to identify the phase and composition of the films. The work function of films showed variation of about 1 eV depending on the oxygen content of the sputter gas while the Fermi level position in the band gap was invariant towards different deposition parameters. Optical transmission spectroscopy in the UV/VIS/NIR regime showed two optical transitions at 0.8 eV and 1.7 eV. However, the optical absorption from these transition does not seem to aid in the conduction of charge carriers as has been revealed by conductivity measurements in a linear 4-point-setup. Diodes were prepared in a glass   FTO      NiO  Au-stacking geometry. They show poor photovoltaic behaviour with a short-circuit current of 0.33 mA cm−1 and an open-circuit voltage of 0.15 V, resulting in an overall efficiency of . The limitation of as an absorber in an All-Oxide solar cell can be related to poor transport properties combined with defect states in the band gap and Fermi level pinning at interfaces. [ABSTRACT FROM AUTHOR]