Pyridalthiadiazole-Based Molecular Chromophores for Defect Passivation Enables High-Performance Perovskite Solar Cells.

Abstract

Passivation of defects at the surface and grain boundaries of perovskite films has become one of the most important strategies to suppress nonradiative recombination and improve optoelectronic performance of perovskite solar cells (PSCs). In this work, two conjugated molecules, abbreviated as CPT and SiPT, are designed and synthesized as the passivator to enhance both efficiency and stability of PSCs. The CPT and SiPT contain pyridalthiadiazole (PT) units, which can coordinate with undercoordinated Pb2+ at the surface and grain boundaries to passivate the defects in perovskite films. In addition, with the incorporation of CPT, the crystallized perovskite films exhibit more uniform grain size and smoother surface morphology relative to the control ones. The efficient passivation by CPT also results in better charge extraction and less carrier recombination in PSCs. Consequently, the CPT-passivated PSCs yield the highest power conversion efficiency (PCE) of 23.14% together with better storage stability under ambient conditions, which is enhanced relative to the control devices with a PCE of 22.14%. Meanwhile, the SiPT-passivated PSCs also show a slightly enhanced performance with a PCE of 22.43%. Our findings provide a new idea for the future design of functional passivating molecules towards high-performance PSCs.