Managing Non-radiative Losses via Energy Alignment and Defect Passivation Using Dual-Functionality Hole-Transporting Materials in Inverted Perovskite Solar Cells

Abstract Interfaces significantly influence both the power conversion efficiency and long-term stability of perovskite solar cells (PSCs). Small-molecule hole-transporting materials (HTMs) are particularly attractive due to their structural tunability, advantageous electronic properties, and thermal stability, all of which contribute to enhanced device durability. This study reports the rational design of asymmetric small-molecule HTMs featuring donor-acceptor-donor (DKO) and donor-acceptor-acceptor (DKCN) architectures. The study examines defect passivation by central Lewis-base functionalities in HTMs and improved charge extraction in mixed-halide PSCs. Photoluminescence and X-ray photoelectron spectroscopy demonstrate that Lewis-base sites coordinate with undercoordinated Pb2+ centers, thereby reducing trap-state density, suppressing interfacial nonradiative recombination, and enhancing charge migration. Side-arm engineering is employed to optimize energy-level alignment and hole-transport properties. DKO exhibits superior hole mobility and more favorable interfacial energetics. Consequently, DKO-based PSCs achieve a power conversion efficiency of 22.85%, representing a 7.5% relative improvement over DKCN (21.25%). This enhancement is primarily attributed to a 6.3% increase in short-circuit current density (JSC: 24.47 vs 23.01 mA cm–2). These findings indicate that integrating Lewis-base functionalization with asymmetric molecular design provides a dual-function strategy for defect passivation and interfacial charge regulation, offering a scalable molecular approach for developing high-performance, stable PSCs.