Self‐Assembled 1D/3D Perovskite Heterostructure for Stable All‐Air‐Processed Perovskite Solar Cells with Improved Open‐Circuit Voltage

Environmental instability and photovoltage loss induced by defects are inevitable obstacles in the development of all-air-processed perovskite solar cells (PSCs). In this study, the ionic liquid 1-ethyl-3-methylimidazolium iodide ([EMIM]I) is introduced into the hole transport layer/three-dimensional (3D) perovskite interface to form a self-assembled 1D/3D perovskite heterostructure, which significantly reduces iodine vacancy defects and modulates band energy alignment, resulting in pronouncedly improved open-circuit voltage (Voc ). As a result, the corresponding device exhibits a high power conversion efficiency with negligible hysteresis and a high Voc of 1.14 V. Most importantly, together with the high stability of the 1D perovskite, remarkable high environmental and thermal stabilities of the 1D/3D PSC devices are achieved, which maintain 89 % of unencapsulated device initial efficiency after 1320 h in air and retain 85 % of the initial efficiency when heated at 85 °C for 22 h. This study affords an effective strategy to fabricate high-performance all-air-processed PSCs with outstanding stability.