Efficient hole transport materials based on naphthyridine core designed for application in perovskite solar...

Naphthyridine-based compounds with a donor-acceptor-donor (D-A-D) skeleton were considered as hole transport materials (HTMs) for perovskite solar cells (PSCs). The optical characteristics, stability, solubility, Hirshfeld surface analysis, crystal structure, and hole transport properties of the HTMs were studied systematically. The HOMO energies of all HTMs were higher than valence band of CH₃NH₃PbI₃ (MAPbI₃) perovskite signifying naphthyridine-based HTMs had appropriate energy alignments for usage in PSCs. The LUMO level of designed HTMs were higher than MAPbI₃ conduction band ensuring prevention of backward electronic movement from MAPbI₃ to the cathode. The λ_abs^max amounts of all HTMs were close 400 nm, which showed their competition with perovskite was impossible. The 18NP and 26NP HTMs had higher hole mobilities compared to that of the Spiro-OMeTAD. Considering aligned HOMO energies, suitable hole mobilities, satisfactory stability and solubility, 18NP (1,8-Naphthyridine) and 26NP (2,6-Naphthyridine) were introduced as the best HTM materials for PSCs which could replace Spiro-OMeTAD.