Exceeding 20% Efficiency for Highly Efficient and Stable Inverted Perovskite Solar Cells via Sodium Borohydride Induced Interface Engineering
Xianhu Wu, Daomei Wu, Guanglei Cui, Zezhuan Jiang, Chunyi Zhao, Xiangyu Tang, Xuting Dong, Nian Liu, Zewen Zuo, Lingbing Kong, Min Gu
Abstract
Poly(3,4‐ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) is widely used as a hole transport layer in inverted perovskite solar cells (PSCs). However, due to the serious interface defects, imperfect energy level arrangement, and low hole transfer rate between PEDOT:PSS and perovskite, the realization of efficient and stable inverted PSCs is hindered. Herein, ionic salt sodium borohydride is used as an interfacial modifier between PEDOT:PSS and MAPbI 3− x Cl x . NaBH 4 acts as an anchor to bond Pb 2+ to the PEDOT:PSS surface and guides the growth of the perovskite. The champion power conversion efficiency (PCE) of the device based on NaBH 4 ‐PEDOT:PSS reaches 20.21%, which is improved by 27.5% compared with the device based on PEDOT:PSS (15.84%). This PCE is one of the highest in inverted PSCs with PEDOT:PSS as the hole transport layer and MAPbI 3− x Cl x as the active layer. The improved device performance is mainly attributed to the reduced valence band edge of PEDOT:PSS which matches better with the HOMO of MAPbI 3− x Cl x , and the hole transfer rate is increased from 2.65 × 10 10 to 3.69 × 10 10 s −1 . The long‐term stability of the optimized device exceeds 1000 h. This work provides a simple and effective strategy to improve the PCE and stability of inverted PSCs, which is a benefit for future popularization.