Synchronous defect passivation of all-inorganic perovskite solar cells enabled by fullerene interlayer
Yanbo Shang, Lingzhi Zhao, Lingbo Jia, Xingcheng Li, Weitao Lian, Peisen Qian, Muqing Chen, Tao Chen, Yalin Lu, Shangfeng Yang
Abstract
All-inorganic CsPbI<sub>3–<i>x</i></sub>Br<sub><i>x</i></sub> perovskite solar cells (PSCs) are advantageous in terms of high thermal stability, while its efficiency lags behind those of organic-inorganic hybrid perovskite counterparts. Defect passivations have been extensively applied for enhancing efficiency of all-inorganic PSCs, which are mainly based on univocal defect passivation of perovskite layer. Herein, we incorporated a bis-dimethylamino-functionalized fullerene derivative (abbreviated as PCBDMAM) as an interlayer between ZnO electron transport layer (ETL) and all-inorganic CsPbI<sub>2.25</sub>Br<sub>0.75</sub> perovskite layer, accomplishing synchronous defect passivations of both layers and consequently dramatic enhancements of efficiency and thermal stability of PSC devices. Upon spin-coating PCBDMAM onto ZnO ETL, the surface defects of ZnO especially oxygen vacancies can be effectively passivated due to the formation of Zn−N ionic bonds. In addition, PCBDMAM incorporation affords effective passivation of Pb<sub>I</sub> and I<sub>Pb</sub> antisite defects within the atop perovskite layer as well via coordination bonding with Pb<sup>2+</sup>. As a result, the regular-structure planar CsPbI<sub>2.25</sub>Br<sub>0.75</sub> PSC device delivers a champion power conversion efficiency (PCE) of 17.04%, which surpasses that of the control device (15.44%). Moreover, the PCBDMAM-incorporated PSC device maintains ~ 80% of its initial PCE after 600 h heating at 85 °C hot plate in N<sub>2</sub> atmosphere, whereas PCE of the control device degrades rapidly to ~ 62% after 460 h heating under identical conditions. Hence, PCBDMAM incorporation benefited dramatic improvement of the thermal stability of PSC device.