Dynamic "On-Demand and Sustainable" Passivation: Light-Heat-Humidity Driven Molecular Isomerization for High-Performance Perovskite Solar Cells.

Abstract

Light, temperature, and humidity are critical external factors triggering phase separation in wide-bandgap (WBG) perovskite solar cells (PSCs). Conventional passivators only achieve static and short-term defect passivation and cannot address the continuously generated dynamic defects and ion migration during device operation. In this work, 1,3,3-trimethylindolino-6-bromobenzopyrylospiropyran (TBS) was introduced into the perovskite bulk. This molecule isomerized into the ring-opened O-TBS structure with abundant active sites under light, heat, and humidity stimuli, thereby enabling on-demand passivation of the device under various environments, ultimately achieving a synergistic balance between static passivation of pristine defects and dynamic repair of newly formed defects. Meanwhile, as a built-in dipole, O-TBS can accelerate carrier extraction and separation, and inhibit phase separation by optimizing the phase structure at the initial stage of nucleation and crystallization. Based on this strategy, a photoelectric conversion efficiency (PCE) of 23.83% was achieved in PSCs with a bandgap of 1.67 eV. Unencapsulated devices retained 91% of their initial efficiency after 1000 h of maximum power point tracking (MPPT) under AM 1.5G illumination, and maintained 88% and 87% of their efficiency after continuous testing for 1000 h at 85°C and 60% humidity, respectively, significantly enhancing the optoelectronic performance and long-term stability of the devices.