Black-phase formamidinium lead iodide (FAPbI 3 ), with a narrow bandgap and high thermal stability, has emerged as an in-demand material for highly efficient perovskite solar cells (PSCs). In a two-step sequential deposition, the PbI 2 film plays an important role in the formation of a perovskite film with desirable qualities. This paper explores using N-methyl-2-pyrrolidone (NMP), a strong Lewis base, and N,N-dimethylformamide (DMF) as a mixed precursor solvent (DMF/NMP) of PbI 2 and reports on preparing PbI 2 films with a porous morphology by thermal treatment. Porous PbI 2 films ensure the diffusion and sufficient reaction of the formamidinium iodide solution to form a smooth perovskite film. In addition, a dynamic spin coating method is also introduced to improve the uniformity of the perovskite film. Both methods yield a pure α-phase FAPbI 3 film immediately in the unannealed state, which is necessary for the perovskite film to maintain phase stability. Finally, PSCs with a power conversion efficiency of 21.20% (0.13 cm 2 ) are fabricated and optimized. The unencapsulated PSCs retain 90% of the initial efficiency for 1000 hours in dry air and exhibit a good thermal stability when heated to 85 °C.
Qianyi Li,Dongyang Li,Zhiqi Li,Qiong Liang,Patrick W. K. Fong,Yu Han,Kuan Liu,Jiangsheng Yu,Peng Bai,Tao Zhu,Yang Bai,Guang Yang,Zhiwei Ren,Gang Li
Hybrid metal halide perovskite solar cells (PSCs) are emerging as highly competitive next-generation photovoltaics due to their excellent performance and low production cost. However, the construction of high-efficiency PSCs typically requires an inert nitrogen environment within a glove box, inadvertently increasing manufacturing costs and hindering the transition from lab-scale to industrial-scale production. In this work, an air ambient fabrication of pure α-phase FAPbI 3 PSCs with high-efficiency and stability, utilizing a dual-functional engineering strategy assisted by 3-Guanidinopropionicacid (3-GuA) is reported. 3-GuA assists in managing excess PbI 2 and promotes the formation of high-quality FAPbI 3 films via intermolecular exchange. Simultaneously, the existence of 3-GuA minimizes the defects and stabilizes the resulting perovskite films. As a result, the ambient-air fabricated PSCs achieve a power conversion efficiency (PCE) of 24.2% with negligible hysteresis and excellent stability. Additionally, these devices demonstrate superior reproducibility, offering valuable guidance for future advancements in this technology.
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