Understanding the Interfacial Reactions and Band Alignment for Efficient and Stable Perovskite Solar Cells Built on Metal Substrates with Reduced Upscaling Losses.

Conventional perovskite solar cells (PSC) built on transparent conductive oxide (TCO) glass face a fundamental challenge to retain fill factor (FF) for large-area upscaling due to series resistance loss. Building a perovskite solar cell on metal has the potential to reduce this FF loss and is promising for flexible applications. However, their efficiency and stability lag far behind their TCO counterparts. Herein, findings on the complex chemical reactions and degradation-promoting processes at different perovskite/metal (Cu, Au, Ag, and Mo) interfaces, which are closely linked with the inherent stability; and the interlayer engineering for perovskite/metal interface's band alignment, which plays an essential role in achieving high efficiency, are reported. Leveraging these findings, 21% power conversion efficiency (PCE) is achieved for 1 cm2 perovskite solar cells using a p-i-n top-illumination structure on a molybdenum substrate, the highest reported for a PSC built on metal. Notably, the FF and PCE losses due to area upscaling are remarkably reduced by one order of magnitude relative to the counterparts on conventional TCO glass, highlighting an alternative pathway for PSC upscaling and module design.

Reducing nonradiative recombination in perovskite solar cells with a porous insulator contact.

Inserting an ultrathin low-conductivity interlayer between the absorber and transport layer has emerged as an important strategy for reducing surface recombination in the best perovskite solar cells. However, a challenge with this approach is a trade-off between the open-circuit voltage (Voc) and the fill factor (FF). Here, we overcame this challenge by introducing a thick (about 100 nanometers) insulator layer with random nanoscale openings. We performed drift-diffusion simulations for cells with this porous insulator contact (PIC) and realized it using a solution process by controlling the growth mode of alumina nanoplates. Leveraging a PIC with an approximately 25% reduced contact area, we achieved an efficiency of up to 25.5% (certified steady-state efficiency 24.7%) in p-i-n devices. The product of Voc × FF was 87.9% of the Shockley-Queisser limit. The surface recombination velocity at the p-type contact was reduced from 64.2 to 9.2 centimeters per second. The bulk recombination lifetime was increased from 1.2 to 6.0 microseconds because of improvements in the perovskite crystallinity. The improved wettability of the perovskite precursor solution allowed us to demonstrate a 23.3% efficient 1-square-centimeter p-i-n cell. We demonstrate here its broad applicability for different p-type contacts and perovskite compositions.

Cs4 PbI6 -Mediated Synthesis of Thermodynamically Stable FA0.15 Cs0.85 PbI3 Perovskite Solar Cells.

The stability issue is still one of the main limitations of the commercialization of perovskite photovoltaics. The mixed cation FAx Cs1 -x PbI3 has shown great promise owing to its improved thermal and moisture stability. However, the study of FAx Cs1 -x PbI3 is concentrated on formamidine (FA)-rich perovskite, whereas cesium (Cs)-rich FAx Cs1 -x PbI3 perovskites are barely studied due to the inevitable phase separation when Cs > 30 mol%. Here, a Cs4 PbI6 -mediated method is developed to synthesize Cs-rich FAx Cs1 -x PbI3 perovskites. It is demonstrated that Cs4 PbI6 intermediate phase has a low Cs cation diffusion barrier and therefore offers a fast ion exchange with the preformed FA-rich perovskite phase to finally form the Cs-rich FAx Cs1 -x PbI3 perovskite. The results indicate that ≈15% alloying with organic FA cations can sufficiently stabilize the perovskite phase with excellent phase and UV-irradiation stability. The FA0.15 Cs0.85 PbI3 perovskite solar cells achieve a champion power conversion efficiency of 17.5%, showing the great potential of Cs-based perovskites for efficient and stable solar cells.

Photo-Supercapacitors Based on Third-Generation Solar Cells.

Photopowered energy systems (PPESs), which simultaneously achieve power conversion and energy storage, are one of the most promising auxiliaries to fulfill the giant and diversified power demand in modern society. Devices with a low cost, wearable, compact structure and the potential to add a variety of features (such as photochromic, flexible, textile, and wearable) have received extensive research attention. Photo-supercapacitors are becoming one of the most extensively researched PPESs due to their ease of fabrication, mitigation of solar irradiation discontinuities, and the promotion of renewable energy utilization, and these devices have been fabricated with different combinations of photovoltage devices and energy-storage technologies. This review summarizes the development of photo-supercapacitors that integrate third-generation solar cells and supercapacitors, with a focus on materials alignment, performance, structure design, and application. Finally, current challenges, possible solutions, and future perspectives are discussed.

A Scalable Methylamine Gas Healing Strategy for High-Efficiency Inorganic Perovskite Solar Cells.

An easy and scalable methylamine (MA) gas healing method was realized for inorganic cesium-based perovskite (CsPbX3 ) layers by incorporating a certain amount of MAX (X=I or Br) initiators into the raw film. It was found that the excess MAX accelerated the absorption of the MA gas into the CsPbX3 film and quickly turned it into a liquid intermediate phase. Through the healing process, a highly uniform and highly crystalline CsPbX3 film with enhanced photovoltaic performance was obtained. Moreover, the chemical interactions between a series of halides and MA gas molecules were studied, and the results could offer guidance in further optimizations of the healing strategy.