With the assistance of a ferroelectric field created by a ferroelectric polymer, the performance of perovskite photo transistors is significantly improved.

Quasi-2D perovskites have attracted extensive attention due to their extraordinary stability compared to their 3D counterparts. Presently, the bottleneck in quasi-2D perovskite solar cells is their relatively low efficiency. The intrinsic interior carrier transport in the perovskite layer consisting of disorderly oriented phases and inadequate optimization of interfacial carrier transfer have greatly limited the overall device performance. A comprehensive study on effective phase manipulation in the BA2MA4Pb5I16 (n = 5) quasi-2D perovskites is presented to pursue optimal efficiency. With the assistance of the solvent DMSO in a constant thermal-annealing spin-coating (CTAS) process, the crystalline growth process in the quasi-2D perovskite film is effectively manipulated and delicate energy band alignment by eliminating the n ≤ 2 phases at the bottom surface has been successfully achieved. Consequently, a significant improvement of carrier transport in the perovskite layer and photogenerated hole extraction at the interface has been accomplished. The champion device exhibited a boosted PCE of 17.66%.

Volatile A-cation halide (AX) additives like formamidinium chloride (FACl) and methylammonium chloride (MACl) have been widely employed for high-efficiency perovskite solar cells (PSCs). However, it remains unstudied how they influence the perovskite film stoichiometry and the solar cell performance and operational stability. Hereby, our work shows that over-annealing of FACl-containing perovskite films leads to a Pb-rich surface, resulting in a high initial efficiency, which however decays during maximum power point tracking (MPPT).On the contrary, perovskite films obtained by a shorter annealing time at the same temperature provide good stability during MPPT but a lower initial efficiency. Thus, we deduce an optimal annealing is vital for both high efficiency and operational stability, which is then confirmed in the case where MACl additive is used. With optimized perovskite annealing condition, we demonstrate efficient and stable p-i-n PSCs that show a best PCE of 20.7% and remain 90% of the initial performance after a 200-hour MPPT at 60 °C under simulated 1-sun illumination with high UV content. Our work presents a comprehensive understanding on how volatile AX impact perovskite film stoichiometry and its correlation to the device performance and operational stability, providing a new guideline for fabricating high-efficiency and operational stable PSCs.