Optimization of P3CPenT-based hole transport layers to boost efficiency in perovskite solar cells

The development of efficient hole transport materials (HTMs) is essential for improving charge extraction and overall performance in perovskite solar cells (PSCs). In this work, three donor–acceptor derivatives, P3CPenT-1, P3CPenT-2, and P3CPenT-3, were designed from the reference P3CPenT molecule and investigated using DFT and TD-DFT calculations at the PBEPBE/6-311G(d,p) level. The designed molecules exhibited reduced HOMO–LUMO energy gaps (2.00–2.30 eV) compared with the reference P3CPenT (3.00 eV), indicating enhanced charge-transfer characteristics. Their absorption maxima were significantly red-shifted from 369.84 nm for P3CPenT to 551.07, 539.51, and 620.20 nm for P3CPenT-1, P3CPenT-2, and P3CPenT-3, respectively. Frontier molecular orbital, density of states, molecular electrostatic potential, and transition density matrix analyses revealed efficient intramolecular charge transfer and charge separation. Energy-level alignment with MAPbI₃ suggested favorable hole extraction and electron-blocking characteristics. Among the investigated systems, P3CPenT-1 exhibited the most promising photovoltaic descriptors, with Voc = 1.0965 eV, FF = 89.02%, and a theoretical PCE descriptor of 20.80%. These findings provide useful insights into the rational design of organic HTMs for next-generation PSCs.