Theoretical Investigation on Carbazole Derivatives as Charge Carriers for Perovskite Solar Cell

Abstract

The study explores carbazole-based organic molecules as transport layers in durable perovskite solar cells, focusing on their optoelectronic and charge transfer properties. Thirteen carbazole derivatives are systematically analyzed via density functional theory (DFT) calculations to understand their structure and optoelectronic characteristics. Substituents like bromo, phenyl, thiophenyl, and pyridyl at positions 3,6- and 2,7- of carbazole were studied. Phenyl and thiophenyl substitutions lowered highest occupied molecular orbital (HOMO) energy levels, while bromo and pyridyl increased them, tuning HOMO energies from −5.45 to −6.03 eV. These energies align well with perovskite materials valence bands, with absorbance primarily below 400 nm, complementing perovskite absorption. The compounds showed high light-harvesting efficiencies (LHEs) (0.22 to 0.94) and improved radiative lifetimes. Theoretical investigations identified most compounds as effective p-type hole-transport materials (HTM), except 3,6- and 2,7-dithiophenyl carbazoles, which exhibited n-type behavior due to low hole reorganization energies. Overall, the study highlights computational design's role in developing carbazole derivatives as promising charge carrier precursors for perovskite solar cells.