Reconstruction of Hole Transport Layer via Co-Self-Assembled Molecules for High-Performance Inverted Perovskite Solar Cells

Adjusting the hole transport layer (HTL) to optimize its interface with perovskite is crucial for minimizing interface recombination, enhancing carrier extraction, and achieving efficient and stable inverted perovskite solar cells (PSCs). However, as a commonly used HTL, the self-assemble layer (SAM) of [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl] phosphonic acid (MeO-2PACz) tends to form clusters and micelles during the deposition process, leading to inadequate coverage of the ITO substrate. Here, a Co-SAM strategy is employed by incorporating 4-mercaptobenzoic acid (SBA) and 4-trifluoromethyl benzoic acid (TBA) as additives into MeO-2PACz to fabricate a Co-SAM-based HTL. The introduced additive can interact with MeO-2PACz, facilitating cluster dispersion and thereby enabling better deposition on ITO for improved HTL coverage. Moreover, Co-SAM exhibits superior energy level alignment with perovskite to enhance interfacial contact and improve carrier extraction efficiency as well as promote growth of bottom perovskite grains. As a result, an impressive increase of the power conversion efficiency (PCE) from 21.34% to 23.31% is achieved in the inverted device based on the Co-SAM HTL of MeO-2PACz+TBA while maintaining ≈90% of its initial efficiency under continuous operation at 1-sun.