Suppressing Phase Segregation and Optimizing Interface Carrier Extraction in High‐Efficiency Wide Bandgap Perovskite Solar Cells

ABSTRACT The salts with amine‐group and self‐assembled monolayers (SAMs) have been commonly used as additives and hole‐selective layers (HTLs) to enhance the performance of wide bandgap (WBG) perovskite solar cells (PSCs), which hold great potential to develop low‐cost tandem photovoltaic technology surpassing the Shockley‐Queisser efficiency limit. In this work, a multifunctional additive, 4‐guanidinobenzoic acid hydrochloride (GBAC), was employed to effectively regulate WBG perovskite film crystallization and suppress phase segregation, resulting in enhanced open‐circuit voltage ( V OC ) and phase stability in PSCs. However, the charge transport in WBG PSCs is affected by the interaction between GBAC and SAM. By modulating the interfacial dipole and energy‐level alignment of SAM modified transparent conductive oxide (TCO) substrates, WBG PSC with a bandgap of 1.66 eV obtained the power conversion efficiency (PCE) of 23.12% with a high fill factor (FF) of 85.64%. Moreover, the device retains 94% of its initial PCE after 600 h of maximum power point tracking under one‐sun illumination at room temperature. Finally, a mechanically stacked perovskite/Cu(In, Ga)Se 2 (CIGS) tandem solar cell attains a PCE of 28.81%. This work provides insight of modulating the interaction between additives and SAMs in high‐performance perovskite photovoltaic devices.