The Bimolecular Co‐Modification Strategy for Interface Management Enables High‐Performance Inverted Perovskite Solar Cells Without Pre‐Deposited HTL

Perovskite solar cells fabricated without pre‐deposited hole‐transport layers (HTL‐free PSCs) offer compelling advantages in simplicity and cost. However, their performance and stability are severely limited by non‐radiative recombination at the perovskite/electron‐transport layer (ETL) interface. While mono‐component phenethylammonium (PEA) passivators can passivate surface defects, their limited passivation capacity, inefficient charge transfer, and instability under photothermal stress hinder further advancement. Herein, a bimolecular co‐modification (BCM) strategy by combining a new molecular passivator, tran‐4‐hydroxy‐D‐proline hydrochloride (THDPH), and PEABr to comprehensively manage the perovskite/ETL interface is proposed. Theoretical and experimental analyses reveal that THDPH concurrently interacts with FA + and Pb 2+ through hydrogen bonds and coordination, respectively. This concerted action induces favorable grain reorientation and suppresses non‐radiative recombination on the perovskite surface. Based on this, the BCM strategy effectively improves crystallization quality, passivates surface and bulk defects, and optimizes interfacial energy alignment. Consequently, the HTL‐free BCM PSC achieves a champion power conversion efficiency of 26.55%. BCM devices also demonstrate significantly enhanced operational stability, retaining 90% of their initial efficiency after 1000 h of continuous illumination. The BCM strategy further exhibits good universality across different bandgaps of PSCs (1.68 and 1.85 eV). This work provides an effective and universal interface design strategy for developing high‐performance perovskite photovoltaics.