Interface Modeling of Perovskite/Polymer Heterostructures for Enhanced Charge-Transfer Efficiency in Hybrid Photovoltaic Materials

Perovskite solar cells based on methylammonium lead iodide (MAPbI3) exhibit remarkable photovoltaic performance, where interface engineering with hole transport layers is crucial for optimizing charge transfer and overall interfacial electronic properties. In this work, we present a density functional theory study of the MAPbI3/poly(3-hexylthiophene) (P3HT) hybrid interface, focusing on the role of perovskite surface termination in determining the interfacial stability and electronic structure. We model MAI- and PbI-terminated MAPbI3 surfaces interfaced with P3HT and compare their interfacial electronic properties. Electronic structure calculations reveal distinct differences in orbital hybridization and band alignment: the MAI/m-P3HT interface exhibits weak coupling, whereas the PbI/m-P3HT interface shows stronger hybridization and enhanced charge transfer. Band alignment confirms type-II, hole-selective character in both cases with a more pronounced valence band maximum adjustment for PbI. Charge difference maps, Bader analysis, and local density of states consistently indicate higher charge transfer and stronger electronic coupling for PbI termination. Electrostatic potential offsets and transport parameters further highlight termination-dependent differences, with lighter effective masses at PbI/m-P3HT compared to those at MAI/m-P3HT. These findings provide theoretical insights into interfacial charge-transport mechanisms and offer guidelines for understanding and tuning the electronic structure of perovskite–organic hybrid interfaces.