Charge and Uniformity Modulation Enables Low‐Loss Self‐Assembled Molecule Contacts for Robust Perovskite Photovoltaics

ABSTRACT Self‐assembled molecules (SAMs) served as hole transport layers (HTLs) have dramatically contributed to the advancement of inverted perovskite solar cells (PSCs). However, further enhancement in the power conversion efficiency (PCE) and stability of these PSCs remains challenging due to issues such as inefficient charge transport, non‐uniform distribution of SAMs, and undesirable perovskite growing on SAM substrate. Herein, we demonstrate a stepwise brominating strategy to develop two efficient SAMs, namely (3‐(9‐bromo‐7H‐benzo[c]carbazol‐7‐yl)propyl)phosphonic acid (Br‐3PABCB) and 3‐(5,9‐dibromo‐7H‐benzo[c]carbazol‐7‐yl)propyl)phosphonic acid (2Br‐3PABCB), whose hole transport ability is enhanced by the increase in electron delocalization through C─H···Br interaction and the spatial arrangement is regulated via steric effect. Co‐assembly of Br‐3PABCB (co‐1Br) or 2Br‐3PABCB (co‐2Br) with (4‐(7H‐dibenzo[c,g]carbazol‐7‐yl)butyl)phosphonic acid (4PADCB) yields co‐self‐assembled monolayers (co‐SAMs), which achieve tight adsorption and uniform morphology on indium tin oxide (ITO), thereby regulating perovskite crystal growth and restraining interfacial nonradiative recombination losses. Consequently, the co‐1Br‐based device attains a notable PCE of 26.87% (certified 26.51%), while maintaining excellent thermal and operational stability. Moreover, co‐1Br is extended to fabricate perovskite solar module (PSM) with an aperture area of 13.9 cm 2 , yielding an impressive PCE of 23.03%. This work provides valuable insights for designing favorable SAM contacts to advance the development of high‐performance PSCs.