Theoretical Design of Self-Assembled Hole Transport Materials Based on π-Conjugation Engineering for Inverted Perovskite Solar Cells

Abstract

Tailored self-assembled hole-transporting materials (SA-HTMs) have been shown to be an effective approach to enhance the performance of inverted perovskite solar cells (PSCs). Based on a π-conjugation engineering strategy, we use Ph-4PACz as the molecular backbone and design three novel SA-HTMs (PACNT, PACDC, and PACFT) by introducing naphthyl, acenaphthyl, and anthryl groups, respectively. By combining density functional theory (DFT), time-dependent DFT (TD-DFT), and molecular dynamics (MD) simulations, the effects of conjugated extension on molecular optoelectronic properties, hole transport, and interfacial behavior were systematically investigated. Theoretical results indicate that the introduction of conjugated groups significantly enhances the molecular dipole moment (reaching 2.11 D for PACFT), optimizes energy level alignment, and increases the magnitude of interfacial adsorption energy (-2.11 eV for PACFT). PACFT exhibits the lowest hole reorganization energy (0.163 eV) and the highest hole mobility (1.74×10⁻¹ cm² V⁻¹ s⁻¹), representing an improvement of four orders of magnitude compared to Ph-4PACz, while effectively passivating surface defects on the perovskite. This work demonstrates that extending π-conjugation is an effective strategy for synergistically enhancing the hole transport capability and interfacial stability of SA-HTMs.