Progress in Photovoltaics最新文献

With the improvement of surface passivation, bulk recombination is becoming an indispensable and decisive factor to assess the theoretical limiting efficiency ($�{\eta }_{\lim }$) of crystalline silicon (c-Si) solar cells. In simultaneous consideration of surface and bulk recombination, a modified model of $�{\eta }_{\lim }$ evaluation is developed. Surface recombination is directly depicted with contact selectivity while bulk recombination is revised on the aspects of ideality factor and wafer thickness. The $�{\eta }_{\lim }$ of the double-side silicon heterojunction (SHJ) and double-side tunneling-oxide passivating contact (TOPCon) solar cells are numerically simulated using the new model as 28.99% and 29.19%, respectively. However, the $�{\eta }_{\lim }$ of single-side TOPCon solar cells, the more practicable scenario, is only 27.79%. Besides, the $�{\eta }_{\lim }$ of the double-side SHJ solar cells would exceed the double-side TOPCon solar cells if the recombination parameter of the non-contacted area is higher than 0.6 fA/cm², instead of perfect passivation. Our results are instructive in accurately assessing efficiency potential and accordingly optimizing design strategies of c-Si solar cells.

Compound/silicon heterojunction (SCH) solar cells have been widely studied because of the low parasitic absorption of the window layer, high short-circuit current, and simple preparation process. So far, most reported SCH solar cells are small-area devices. By depositing MoO_x hole transport layer using hot-wire oxidation–sublimation deposition technique and employing a front-contact back-junction cell architecture, the large-area SCH solar cells are successfully fabricated on M6 (166 mm) n-type silicon wafers. Indium cerium oxide (ICO) film with the optimal thickness of about 110 nm is inserted between MoO_x and Ag. The ICO/Ag stack functions well as a back reflector and is beneficial for increasing the short-circuit current density, reducing the contact resistance, and improving the device stability. A power conversion efficiency of 21.59% is achieved on the champion SCH solar cell with the device area of 274.15 cm².

The suitable band gap with outstanding optoelectronic characteristics makes Sn-based perovskites one of the promising candidates for the preparation of efficient lead-free perovskite solar cells (PSCs). However, preparing Sn²⁺-based PSCs is very difficult due to the ready oxidation of Sn²⁺ to Sn⁴⁺ when exposed to air. In this work, by incorporating the trimethylamine borane complex (TMAB) as an antioxidant additive into the perovskite precursor solution along with excess SnF₂, we report the fabrication of air-stable FASnI₃-based solar cells. The complex formed by TMAB-SNF₂ (additive layer) enables in-situ encapsulation of perovskite grains. This layer considerably improves the oxidation stability of the perovskite layer by eliminating oxygen vacancies from the NiO hole transport. The resulting PSCs can maintain more than 70% of the efficiency over 45 and 75 hours respectively in air and N₂ exposure without encapsulation. This can be regarded as a genuinely enhanced attribute, particularly considering the use of carbon in one of the electrodes in FASnI₃ perovskites. The findings suggest an alternative approach to provide effective and sustainable Sn-based PSCs in the future.

The presence of hot carriers is presented in the operational properties of an (FA,Cs)Pb(I, Br, Cl)₃ solar cell at ambient temperatures and under practical solar concentration. Albeit, in a device architecture that is not suitably designed as a functional hot carrier solar cell. At 100 K, clear evidence of hot carriers is observed in both the high energy tail of the photoluminescence spectra and from the appearance of a nonequilibrium photocurrent at higher fluence in light J–V measurements. At room temperature, however, the presence of hot carriers in the emission at elevated laser fluence is shown to compete with a gradual red shift in the PL peak energy as photoinduced halide segregation begins to occur at higher lattice temperature. The effects of thermionic emission of hot carriers and the presence of a nonequilibrium carrier distribution are also shown to be distinct from simple lattice heating. This results in large unsaturated photocurrents at high powers as the Fermi distribution exceeds that of the heterointerface controlling carrier transport and rectification.

Efficient metal contact formation is pivotal for the production of cost-effective, high-performance crystalline silicon (Si) solar cells. Traditionally, screen-printed silver (Ag) contacts on the front surface have dominated the industry owing to their simplicity, high throughput, and significant electrical benefits. However, the high cost associated with using over 13–20 mg/Wp of Ag can impede the development of truly cost-effective solar cells. Therefore, there is an urgent need to explore alternative, economically viable metals compatible with silicon substrates. This study reports on the application of a contact stack consisting of Ag, nickel (Ni), and copper (Cu) in Si solar cells. To prevent Schottky contact formation, Ag is implemented as a seed layer, whereas Ni and Cu form the metal bulk layer. The fabricated bi-layer stack without selective emitter exhibits a maximum efficiency of ~21.5%, a fill factor of 81.5%, and an average contact resistance of 5.88 mΩ·cm² for a monofacial PERC cell. Microstructure analysis demonstrates that the metals within the contacts remain distinct, and Cu diffusion into the silicon during the firing process is absent. Consequently, printed bi-layer contacts emerge as a promising alternative to Ag contacts, reducing the Ag consumption to below 2.5 mg/Wp per cell without compromising overall efficiency.

This work presents a novel paradigm for upconversion-assisted ferroelectric photovoltaic devices. The system comprises a ferroelectric active layer (BiFeO₃), an upconverter layer (Yb; Er-doped ZnO), a conductive ITO-coated glass substrate, and a reflective coating (Al) at the rear end of the glass substrate. The photovoltaic efficiency of the single-layer BFO was found to be 0.71%. With the prescribed device model, the total solar efficiency of BiFeO₃ improved significantly and touched solar conversion efficiency of 2.21%. This model's projection widens the future perspectives of device performance in emerging photovoltaic technology, mainly perovskite-based solar cells.

CuGaS₂ films grown by physical vapor deposition were studied by photoluminescence (PL) spectroscopy, using excitation intensity and temperature-dependent analyses. We observed free and bound exciton recombinations, three donor-to-acceptor (DA) transitions, and deep-level transitions. The DA transitions at ~2.41, 2.398, and ~2.29 eV are attributed to a common donor level ~35 meV and two shallow acceptors at ~75 and ~90 meV and a deeper acceptor at 210 meV above the valence band. This electronic structure is similar to those of other chalcopyrite materials. The observed DA transitions are accompanied by several phonon replicas. The Cu-rich and near-stoichiometric CuGaS₂ films are dominated by transitions involving the acceptor at 210 meV. All films show deep-level transitions at ~2.15 and 1.85 eV due to broad deep defect bands. The slightly Cu-deficient films were dominated by intense transitions at ~2.45 eV, which were attributed to excitonic transitions, and a broad defect transition at 2.15 eV.

Organic photovoltaics (OPV) has attracted tremendous attention as a promising alternative to silicon wafer-based technologies for building integration. While significant progress has been achieved on the power conversion efficiency of OPV technologies, their field stability is rarely studied. This work investigates the field performance and reliability of a large-area OPV module designed for building integration in tropical Singapore for 4.5 years. The device suffered more than 14% degradation in power at the standard testing conditions from the initial performance, largely due to losses in fill factor (−12% relative). During the monitoring period, it exhibited comparable performance to more conventional silicon PV technologies, with an average specific energy yield of about 4 kWh/kWp/day and an average performance ratio of 0.96. Excellent performance at low light conditions was also observed. However, its field performance was heavily impacted by soiling, which typically led to a 5 to 10% loss in the current output after several months. Further, the device's outdoor performance also showed a three-stage degradation process, including (1) an initial slow degradation in the first 2 years (about −1%/year), (2) a stable period with negligible performance loss from Years 2 to 3.5, and (3) a rapid degradation in the last year (about −5%/year).

We provide a comprehensive analysis of the effect of spectral albedo on photovoltaic (PV) module measurements and system model predictions. We demonstrate how to account for albedo in indoor bifacial device measurements by adjusting the applied irradiance using the scaled rear irradiance method, exemplified on fabricated silicon heterojunction (SHJ) modules. System model performance is studied using a detailed 3D finite-element model, DUET, for fixed-tilt and horizontal single-axis tracked (SAT) arrays between 15 and 75°N. Spectral effects cause variations in measured SHJ module short-circuit current up to 2% and efficiency variation up to 0.3% abs. We further demonstrate that rear-side spectral mismatch factors (SMMs) resulting from including or omitting spectral albedo in PV system modeling vary between ±13%, while total (front+rear) SMMs vary up to 3%, depending on the deployment configuration and latitude. SAT array SMMs are weakly correlated with latitude, while fixed-tilt array SMMs increase with latitude, driven by an increasing proportion of ground-reflected light on the front-side of modules. Ground-reflections can constitute between 2% and 32% of total incident module irradiance, with notably high (>10%) contributions for fixed-tilt arrays at high latitude. Effects of spectral albedo are most significant for: (1) fixed-tilt deployments at high latitudes, (2) wide bandgap technologies such as perovskite and cadmium telluride cells, (3) albedos which vary steeply over the technology's absorption range, and (4) high albedo ground covers. Overall, we demonstrate that omitting spectral albedo effects can result in PV measurement and system-level modeling uncertainties on the order of several percent in these cases.