Multiple-cation lead mixed-halide perovskites (MLMPs) have been recognized as ideal candidates in perovskite solar cells in terms of high efficiency and stability due to decreased open-circuit voltage loss and suppressed yellow phase formation. However, they still suffer from an unsatisfactory long-term moisture stability. In this study, phosphorus-containing Lewis acid and base molecules are employed to improve device efficiency and stability based on their multifunction including recombination reduction, phase segregation suppression, and moisture resistance. The strong fluorine-containing Lewis acid treatment can achieve a champion PCE of 22.02%. Unencapsulated and encapsulated devices retain 63% and 80% of the initial efficiency after 14 days of aging under 75% and 85% relative humidity, respectively. The better passivation of Lewis acid implies more halide defects than Pb defects at the MLMP surface. This unbalanced defect type results from phase segregation that is the synergistic effect of Cs and halide ion migrations. Identifying defect type based on different passivation effects is beneficial to not only choose suitable passivators to boost the efficiency and slow down the moisture degradation of MLMP solar cells, but also to understand the mechanism of defect-assisted moisture degradation.

There is strong interest in improving the environmental stability of hybrid perovskite solar cells while maintaining high efficiency. Here, we solve this problem by using epilayers of a wide-band-gap 1D lead iodide perovskitoid structure, based on a short organic cation, namely, thiazole ammonium (TA) in the form of lead iodide (TAPbI3). The 1D capping layer serves to passivate three-dimensional (3D) perovskite films, which promotes charge transport, improves carrier lifetime, and prevents iodide ion migration of the 3D (MA,FA)­PbI3 film (MA = methylammonium, FA = formamidinium). Furthermore, the corresponding device achieved considerable efficiency and better environmental stability than the -based analogue, delivering a champion PCE value of 18.97% while retaining 92% of this efficiency under ambient conditions in air for 2 months. These findings suggest that utilization of a 1D perovskitoid is an effective strategy to improve the environmental stability of 3D-based perovskite solar cell devices maintaining at the same time their high efficiency.

A uniform and full coverage perovskite film is of significant importance for flexible perovskite solar cells.

A ruthenium complex (JK-142) with an ancillary bipyridyl ligand substituted by a 3-carbazole-2-thiophenyl moiety was synthesized and explored as a sensitizer in cosensitized solar cells in combination with an organic dye (JK-62). The extended π-conjugation in the ancillary ligand enables the JK-142 dye to have a red-shift light absorption band; however, the ineffective penetration of JK-142 molecules into the inner surface of TiO 2 film results in low photovoltaic performance for the single dye sensitized solar cell due to its large molecular size of JK-142. Interestingly, when the deficient JK-142 electrode was employed to assemble a cosensitized solar cell by additionally adsorbing JK-62 dye, a considerably improved efficiency of up to 10.2% was achieved, which is favorably superior to that (ca. 8.68%) of N719 in the same device configurations. The results shown here not only provide new vision on how to produce highly efficient solar cells using dyes with extended molecular structure but also open up a new way to position different dyes on a single TiO 2 film for cosensitization through controlling the molecule size.

Control of the perovskite film formation process to produce high-quality organic-inorganic metal halide perovskite thin films with uniform morphology, high surface coverage, and minimum pinholes is of great importance to highly efficient solar cells. Herein, we report on large-area light-absorbing perovskite films fabrication with a new facile and scalable gas pump method. By decreasing the total pressure in the evaporation environment, the gas pump method can significantly enhance the solvent evaporation rate by 8 times faster and thereby produce an extremely dense, uniform, and full-coverage perovskite thin film. The resulting planar perovskite solar cells can achieve an impressive power conversion efficiency up to 19.00% with an average efficiency of 17.38 ± 0.70% for 32 devices with an area of 5 × 2 mm, 13.91% for devices with a large area up to 1.13 cm(2). The perovskite films can be easily fabricated in air conditions with a relative humidity of 45-55%, which definitely has a promising prospect in industrial application of large-area perovskite solar panels.