Synergistic experimental and theoretical investigation of carbazole–cyanopyridine-based hole-transporting materials

Abstract

This work highlights the design, synthesis, and characterization of three new hole-transporting materials (, , and ) based on donor–acceptor–donor (D–A–D) and acceptor–acceptor–donor (A–A–D) concepts. Crystals of two compounds, and , were obtained under similar crystallization conditions. The molecular structures were thoroughly examined using DFT, photophysical, electrochemical, and thermal methods. The UV-vis absorption spectrum of displayed a significant bathochromic effect compared to its counterparts and . This could be because the thiophene units enhance conjugation and lead to a bathochromic shift. Compared to (1.7 × 10⁻⁵ cm² V⁻¹ s⁻¹) and (1.6 × 10⁻⁵ cm² V⁻¹ s⁻¹), was found to have a higher hole mobility value of 2.1 × 10⁻⁵ cm² V⁻¹ s⁻¹. To further explain and complement the experimental data, DFT calculations of the geometry, electronic structure, absorption, reorganization energy, transition density matrix, and density of states of compounds were performed. These characteristics make it abundantly evident that compounds based on carbazoles and cyanopyridines are very attractive materials for use as hole-transporting materials in perovskite solar cells.