Highly stable and Efficient Perovskite Solar Cells Based on FAMA‐Perovskite‐Cu:NiO Composites with 20.7% Efficiency and 80.5% Fill Factor

To solve critical issues related to device stability and performance of perovskite solar cells (PSCs), FA0.026MA0.974PbI3−yCly‐Cu:NiO (formamidinium methylammonium (FAMA)‐perovskite‐Cu:NiO) and Al2O3/Cu:NiO composites are developed and utilized for fabrication of highly stable and efficient PSCs through fully‐ambient‐air processes. The FAMA‐perovskite‐Cu:NiO composite crystals prepared without using any antisolvents not only improve the perovskite film quality with large‐size crystals and less grain boundaries but also tailor optical and electronic properties and suppress charge recombination with reduction of trap density. A champion device based on the composites as light absorber and Al2O3/Cu:NiO interfacial layer between electron transport layer and active layer yields power conversion efficiency (PCE) of 20.67% with VOC of 1.047 V, JSC of 24.51 mA cm−2, and fill factor of 80.54%. More importantly, such composite‐based PSCs without encapsulation show significant enhancement in long‐term air‐stability, thermal‐ and photostability with retaining 97% of PCE over 240 d under ambient conditions (25–30 °C, 45–55% humidity). Formamidinium methylammonium (FAMA)‐perovskite‐Cu:NiO and Al2O3/Cu:NiO composites are developed for highly stable and efficient perovskite solar cells. The composites not only improve the perovskite film quality but also suppress charge recombination with substantial reduction of trap density. The composites based devices yielded power conversion efficiency of 20.7% with fill factor of 80.5%. More importantly, unencapsulated cells showed significant enhancement of air‐stability, thermal‐ and photo‐stability with retaining 97% of PCE over 240 days under ambient conditions.