Tuning the long-range corrected functional for accurate excited-state spectroscopic, charge transport, and interfacial insights into D-π-D type hole transport materials

The development of small molecule hole transport materials (HTMs) with high flatness through reasonable molecular design to regulate the interfacial interaction and charge transport of perovskite solar cells (PSCs) has become a current research hotspot. This study used the high-performance small molecule ST as a reference, and systematically designed a series of HTMs (ST1, ST2, ST3) by introducing pyrene, benzopyrene, and dibenzopyrene as π-bridges to modulate the planarity of the π-bridge. The results show that ST1 with a π-bridge of pyrene and ST2 with a π-bridge of benzopyrene achieved better energy level matching with the perovskite material, while ST3 with a π-bridge of dibenzopyrene exhibited the optimal ionization potential, solvation free energy, and total charge transfer. For excited states, we adjusted the range-separation parameter ω in the long-range corrected functional LC-ωPBE to accurately characterize the optical bandgap and excited-state properties of the molecules. The highest absorption peaks of the three designed molecules show a clear blue shift compared to ST, effectively avoiding the competition in light absorption between the HTM layer and the perovskite active layer. Migration analysis shows that ST1, ST2, and ST3 all exhibit higher migration rates than ST. Interface analysis indicates that the molecule ST3 achieves the optimal interfacial adsorption energy and Bader charge-transfer amount. This work provides important guiding principles for the rational design of HTMs for PSCs.