Penetrative and Homogenized Surface Passivation for Evaporation‐Solution‐Processed Perovskite Solar Cells via a Synergistic Bimolecular Strategy

Abstract Perovskite solar cells (PSCs) have garnered significant attention for their outstanding optoelectronic properties, yet surface defects remain a major obstacle to achieving optimal performance, especially in scalable hybrid evaporation‐solution fabrication methods. Conventional passivation techniques often struggle with shallow penetration of passivation agents, limiting their effectiveness. Here, an advanced post‐treatment strategy is introduced that synergistically combines 2‐thiopheneethylammonium chloride with a trace amount of ethylenediamine to achieve superior surface passivation. ethylenediamine acts as a “penetration facilitator,” mildly etching the perovskite surface and enabling deeper infiltration of 2‐thiopheneethylammonium chloride, which results in the formation of a uniformly distributed and pure‐phase 2D perovskite layer. This deeply penetrating passivation layer effectively suppresses nonradiative recombination at the perovskite/electron transport layer interface. As a result, inverted PSCs fabricated using the hybrid evaporation‐solution method achieved a power conversion efficiency of 24.20%, accompanied by an open‐circuit voltage of 1.189 V and an open‐circuit voltage deficit of 0.36 V. Additionally, this post‐treatment strategy demonstrates broad performance enhancements across PSCs with various bandgaps and fabrication methods, offering a versatile and promising pathway to boost both the efficiency and stability of PSCs.