Progress in Photovoltaics最新文献

Ultrathin solar cells are efficient and captivating devices with unique technological and scientific features in terms of minimal material consumption, fast fabrication processes, and good compatibility with semi-transparent applications. Such photovoltaic (PV) technologies can enable effective synergy between optical and electronic confinements with large tuning capabilities of all the optoelectronic characteristics. In this work, the implications of the optical design and the bandgap engineering in ultrathin hydrogenated amorphous Si/Ge multiple quantum well (MQW) solar cells featuring photonic nanocavity are analyzed based on experimental measurements and optoelectronic modelling. By changing the period thicknesses and the positions of QWs inside the deep-subwavelength nanophotonic resonator, the spatial and spectral distributions of the optical field and the local absorption are strongly affected. This leads to a modulation of the absorption resonance condition, the absorption edge and the resulting photocurrent outputs. Because of quantum confinement effect, the change of MQW configurations with different individual QW periods while keeping similar total thickness of about 20 nm alters both the bandgap energy and the band offset at the QW/barrier heterojunctions. This in turn controls the photovoltage as well as the carrier collection efficiency in solar cells. The highest open circuit voltage and fill factor values are achieved by employing MQW device configuration with 2.5 nm-thin QWs. A record efficiency above 5.5% is reached for such emerging ultrathin Si/Ge MQW solar cell technology using thinner QWs with sufficient number, because of the optimum trade-off between all the optoelectronic characteristic outputs. The presented design rules for opaque ultrathin solar cells with quantum-confined nanostructures integrated in a photonic nanocavity can be generalized for the engineering of relevant multifunctional semitransparent PV devices.

As PV manufacturing heads towards the multi-TW scale, it is required to carefully evaluate a wide range of concepts including not only efficiency and cost but also material consumption to ensure sustainable manufacturing of PV technologies. The rapid growth of PV could significantly increase the demand for several materials required in solar cells such as silver, aluminium, copper and even silicon, thereby causing dramatic price fluctuations. Furthermore, the PV manufacturing capacity would be at risk of being limited by the supply of some scarce metals, e.g. with current industrial implementations – screen printing (SP) metallization, the capacities of PERC and TOPCon could be capped at 377 GW and 227 GW with 20% of global silver supply available to the PV industry. In addition, PV systems have ~25–30 years lifespan to ensure low LCOE and emissions. Recycling alone will not provide an immediate solution to overcome the limitation of material consumption in the exponentially growing PV market. It is expected that the Ag usage needs to be reduced to no more than 5 mg/W or even 2 mg/W for all solar cell technologies to allow a multi-TW manufacturing scale without depleting the global silver supply. Therefore, further advancements in metallization technologies are critically and urgently required to significantly reduce the silver consumption of current screen-printed contacts in industrial silicon solar cells. This paper firstly presents a roadmap towards the 5 mg/W and 2 mg/W silver consumption targets with various metallization technologies and screen-printing designs. Subsequently, a hybrid plating on screen-printed metallization design was proposed to improve the performance and reduce the silver consumption of screen-printed contacts. The experimental results have demonstrated up to 1.08%_abs improvements in fill factor and 0.3%_abs gains in cell efficiency. In addition, up to 40%_rel reductions in finger silver consumption have been achieved without any sacrifices in the electrical conductivity of such hybrid screen-printed and plated fingers. This work proposes not only a roadmap but also a promising approach to significantly reduce the Ag demand and benefit sustainable production of industrial screen-printed silicon solar cells in the TW era.

In May 2022, the European Commission adopted a new European Union (EU) Solar Energy Strategy [1] aiming to ensure that solar energy achieves its full potential in helping to meet the European Green Deal's climate and energy targets. A goal of the strategy is to reach nearly 600 GW of installed solar photovoltaics (PV) capacity by 2030. While Europe is a pioneer in the definition of new policy requirements to ensure the circularity and sustainability of PV products, its manufacturing capabilities are limited. The EU mostly imports PV modules from China, which for the last decade has remained the global leader in PV manufacturing across the supply chain. This article aims to provide insight into the solar PV industry and the surrounding policy context, focusing on the manufacturing phase and its climate impact. It provides a comparative overview of the key players in the European and Chinese PV markets with an overview of the whole supply chain (i.e. production of polysilicon, cells, wafers and modules). Having in mind the net-zero commitments across the globe, and a central role of the solar PV in the energy transition, the demand for PV products is expected to grow exponentially in the next decades. With this in mind, the authors look into environmental impacts from the PV manufacturing. A simplified analysis concludes on the suitability of the PV manufacturing process today and indicates the opportunities for the net-zero transition in the future. While the focus is on the carbon impacts of the solar PV industry, the authors also identify other relevant aspects (such as circularity), laying the ground for a future research.

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.