• Energy Research

Molybdenum oxide (MoOX) combines a high work function with broadband optical transparency. Sandwiched between a hydrogenated intrinsic amorphous silicon passivation layer and a transparent conductive oxide, this material allows a highly efficient hole‐selective front contact stack for crystalline silicon solar cells. However, hole extraction from the Si wafer and transport through this stack degrades upon annealing at 190 °C, which is needed to cure the screen‐printed Ag metallization applied to typical Si solar cells. Here, we show that effusion of hydrogen from the adjacent layers is a likely cause for this degradation, highlighting the need for hydrogen‐lean passivation layers when using such metal‐oxide‐based carrier‐selective contacts. Pre‐MoOX‐deposition annealing of the passivating a‐Si:H layer is shown to be a straightforward approach to manufacturing MoOX‐based devices with high fill factors using screen‐printed metallization cured at 190 °C.

Abstract Despite impressive power conversion efficiencies (PCEs) reported for lab-scale perovskite solar cells (PSCs), obtaining large-area devices with similar performance remains challenging. Fundamentally, this can largely be attributed to a polarity mismatch between the perovskite-precursor solution and the underlying hydrophobic contact materials, resulting in perovskite films of insufficient quality for scaled devices. Specifically, for p-i-n devices, the commonly used DMF/DMSO co-solvent has a significant polarity mismatch with its underlying hole-transporting layer, PTAA. Here, the role of MAPbI3•solvent adduct interaction with the PTAA surface towards the formation of micro- and nano-scale pinholes is elucidated in detail. Replacing DMSO with NMP in the co-solvent system changes the binding energy profoundly, enabling uniform and dense films over large areas. The PCE of DMF/NMP ink-based devices drops slightly with increasing active device area, from 21.5% (0.1 cm2) to 19.8% (6.8 cm2), in comparison with conventional DMF/DMSO ink. This work opens a pathway towards the scalability of solution-processed perovskite optoelectronic devices.

ABSTRACTMonolithic perovskite/perovskite/silicon triple‐junction solar cells have the potential to exceed the efficiency limits of perovskite/silicon dual‐junction solar cells. However, the development of perovskite/perovskite/silicon triple‐junction technology faces several significant hurdles, including the development and integration of a stable high bandgap perovskite absorber into the monolithic structure. Key issues include light‐induced halide segregation in mixed halide high bandgap perovskites and the risk of solvent damage to underlying layers during top‐cell deposition. To overcome these challenges, we developed a high bandgap, inorganic perovskite absorber, CsPbI2Br, using thermal evaporation at room temperature, eliminating the need for post‐deposition annealing. The resulting perovskite films exhibited a bandgap of 1.88 eV and demonstrated good photostability without any signs of halide segregation under continuous illumination probed over 3 h. Additionally, thermal evaporation offers a scalable approach for large‐scale production, further enhancing the potential for widespread adoption of this technology. This advancement enabled the incorporation of CsPbI2Br perovskite films into a monolithic perovskite/perovskite/silicon triple‐junction device as the top‐cell absorber. Consequently, we developed the first triple‐junction device with an all‐inorganic perovskite top‐cell absorber using the thermal evaporation technique, achieving an efficiency of 21%, with an open‐circuit voltage of 2.83 V over an active area of 1 cm2. The device underwent 100 h of fixed voltage measurement near maximum power point under ambient conditions without encapsulation. Remarkably, it not only withstood the measurement but also exhibited an improved efficiency of ~22% afterwards, further demonstrating the stability and reliability of our thermally evaporated CsPbI2Br perovskite absorber‐based inorganic solar cell for monolithic triple‐junction perovskite/perovskite/silicon applications.

Highly-transparent carrier-selective front contacts open a pathway towards entirely dopant free Si solar cells. Hole selective a-Si:H/MoOx/ITO front contact stacks were already successfully applied in such novel devices. However, for optimum device performance, further improvements are required: We evaluate the use of the high-work-function material WOX as a replacement for MoOx in an attempt to reduce optical absorption losses. In addition, we investigate the use of thin hydrogenated SiOX instead of a-Si:H, and the impact of the residual pressure for MoOx evaporation.

Abstract We report on the performance of Silicon Heterojunction (SHJ) solar cell under high operating temperature and varying irradiance conditions typical to desert environment. In order to define the best solar cell configuration that resist high operating temperature conditions, two different intrinsic passivation layers were tested, namely, an intrinsic amorphous silicon a-SiO x :H with CO 2 /SiH 4 ratio of 0.4 and a-SiOx:H with CO 2 /SiH 4 ratio of 0.8, and the obtained performance were compared with those of a standard SHJ cell configuration having a-Si:H passivation layer. Our results showed how the short circuit current density J sc , and fill factor FF temperature-dependency are impacted by the cell’s configuration. While the short circuit current density J sc for cells with a-SiO x :H layers was found to improve as compared with that of standard a-Si:H layer, introducing the intrinsic amorphous silicon oxide (a-SiO x :H) layer with CO 2 /SiH 4 ratio of 0.8 has resulted in a reduction of the FF at room temperature due to hindering the carrier transport by the band structure. Besides, this FF was found to improve as the temperature increases from 15 to 45 °C, thus, a positive FF temperature coefficient.

Despite great progress in perovskite/silicon tandem solar cells’ device performance, their susceptibility to potential-induced degradation (PID) remains unexplored. In this study, we find that applying a voltage bias of −1,000 V to single-device perovskite/silicon tandem modules at 60°C for ∼1 day can cause a ∼50% loss in their power conversion efficiency, which raises concerns for tandem commercialization. We found no accumulation of Na+ in the perovskite or silicon photon absorbers. Consequently, no obvious shunt is observed in our silicon subcells. We also find that elements diffuse from the perovskite into the module encapsulant during PID testing. We argue that this diffusion is the main PID mechanism in our tandem modules. While applying a large positive voltage bias can partially recover this PID, introducing barriers or structures to prevent elemental diffusion out of the perovskite may be required to mitigate this degradation phenomenon. ; This work was supported by the King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under award nos. OSR-2021-4833, OSR-CARF/CCF-3079, IED OSR-2019-4580, OSR-CRG2020-4350, CRG2019-4093, and IED OSR-2019-4208.

Monolithically integrated two-terminal perovskite/Si tandem solar cells promise to achieve high power conversion efficiency. However, there is a concern that the stability of the perovskite top cell will limit the long-term performance of tandem devices. To investigate the impact of perovskite cell degradation on the photocurrent generation and collection in the individual subcells, we employed light beam induced current mapping to spatially resolve the photocurrent under controlled humidity conditions. The evolution of the device behavior is consistent with the formation of an optically transparent hydrated perovskite phase that allows the bottom Si cell to continue to generate photocurrent at the probing wavelength (532 nm). Additional measurements were performed on perovskite thin films on glass substrates to verify the interpretation.