Stabilization of <i>α</i>‐phase FAPbI<sub>3</sub> via Buffering Interfacial Region for Efficient p–i–n Perovskite Solar Cells
Yulan Huang, Bingzhe Wang, Tanghao Liu, Dongyang Li, Yujie Zhang, Tianqi Zhang, Xiyu Yao, Yun Wang, Abbas Amini, Yongqing Cai, Baomin Xu, Zikang Tang, Guichuan Xing, Chun Cheng
Abstract
Abstract Formamidinium lead triiodide (FAPbI 3 ) with an ideal bandgap and good thermal stability has received wide attention and achieved a record efficiency of 26% in n–i–p (regular) perovskite solar cells (PSCs). However, imperfect FAPbI 3 formation on the typical hole transport layer (HTL), high interfacial trap‐state density, and unfavorable energy alignment between the HTL and FAPbI 3 result in the inferior photovoltaic performance of p–i–n (inverted) PSCs with FAPbI 3 absorber. Herein, the α ‐phase FAPbI 3 is stabilized by constructing a buffer interface region between the NiO x HTL and FAPbI 3 , which not only diminishes NiO x /FAPbI 3 interfacial reactions and defects but also facilitates carrier transport. Upon the construction of a buffer interface region, FAPbI 3 inverted PSC exhibits a high‐power conversion efficiency of 23.56% (certified 22.58%) and excellent stability, retaining 90.7% of its initial efficiency after heating at 80 °C for 1000 h and 84.6% of the initial efficiency after operating at the maximum power point under continuous illumination for 1100 h. Besides, as a light‐emitting diode device, the FAPbI 3 inverted PSC can be directly lit with an external quantum efficiency of 1.36%. This study provides a unique and efficient strategy to advance the application of α ‐phase FAPbI 3 in inverted PSCs.