Modeling electronic structure and charge transport properties of Tetrathienopyrrole-based hole-transporting materials: A DFT approach for enhanced photovoltaic efficiency towards efficient perovskite solar cells

Abstract

This quantum mechanical approach paved the way for fabricating highly stable hole-transporting materials for photovoltaic cells. This scheme involved the integration of acceptor terminal units through a thiophene spacer to the versatile symmetrical tetrathienopyrrole core connected to dimethoxytriphenylamine helix units, resulting in a series of six novel HTMs (DTT-1 to DTT-6). Comprehensive analysis of the energetics of energy levels (HOMO/LUMO), solvation energy, density of states (DOS), and stability of proposed HTMs were evaluated by systematically performing the quantum computation via (DFT) and (TD-DFT). The results revealed that fabricated HTMs (DTT-1 to DTT-6 unveiled stabilized HOMO levels approaching the edge with suitable HTM/perovskite energy level alignment, proposing exceptional charge extraction and high open circuit voltage. Photophysical analysis indicated that our fabricated HTMs revealed larger Stokes shift values (75 nm −150 nm) and transparency in the visible region, allowing full utilization of sunlight for the perovskite layer for photocurrent generation and enhanced spectral selectivity. The proposed HTMs showed smaller RE values ranging from 0.106 eV to 0.23 eV and greater transfer integral, signifying ultrafast hole mobility. Moreover, comparatively higher dipole moments (2.81 D-11.07 D) and higher negative solvation energies (−18.62 kcal/mol to −21.86 kcal/mol) suggested improved solubility and film-forming attributes. Hence, this study provides crucial insights into the deliberate and effective design of high-performance HTMs.