Efficient and Stable Nonfullerene-Graded Heterojunction Inverted Perovskite Solar Cells with Inorganic Ga2O3 Tunneling Protective Nanolayer

Inverted planar perovskite solar cells (PSCs) exhibit advantages in terms of simple device fabrication, good reproducibility, and less hysteresis. However, there still remain challenges to passivate the trap states within the perovskite film and reduce interface instability arising from penetration of moisture and the diffusion of metal electrode. In this work, perovskite passivation is reported using gradiently distributed nonfullerene electron-rich Lewis bases small molecule IDIC (a pi-conjugated Lewis base: indacenodithiophene end-capped with 1.1-dicyanomethylene-3-indanone), which is realized through an antisolvent dropping process. Additionally, an inorganic wide band gap Ga2O3 is introduced as a tunneling nanolayer into interface between the metal electrode and electron transport layer that effectively passivate interface and mitigate moisture and metal ion diffusion. These treatments enable the fabrication of CH3NH3PbI3-based inverted PSCs with excellent power conversion efficiencies up to 19.86% as well as enhanced ambient stability. This work provides new strategies to improve the performance and stability for the inverted PSCs.