Performance Improvement Mechanism of Perovskite Solar Cells by Device Interface Control

Perovskite solar cells are attractive because of their remarkably improved power conversion efficiency (PCE). For their application, controlling the interface state is crucially important to increase PCE. Herein, operando direct observations of spin states in perovskite solar cells using electron spin resonance (ESR) are described, thereby elucidating the interface state from a microscopic viewpoint. Simultaneous measurements of solar cell characteristics and ESR demonstrated that the spin states in the hole‐transporting layer change in accordance with the device‐performance variation under operation. These variations are ascribed to the change of hole transport and to interfacial electric dipole layers. Conducting such operando microscopic investigation is expected to be useful to formulate guidelines for improving device performance and durability.