Effects of cyano-substitutions on the energy storage and optoelectronic properties of hydrazone photoisomerization switch

This work explores the impact of cyano-substitutions on the energy storage and UV–vis spectra of a long half-life photosensitive hydrazone (HDZ) molecular system. The relevance of this study lies in the investigation of properties such as energy storage density, solar spectrum matching, and minimal spectral overlap in the context of enhancing solar energy storage technologies. The results indicate that cyano-substituted systems 4-HDZ-CN, 4-HDZ-(CN)2, and 5-HDZ-(CN)2, all featuring substitution at the phenyl group, significantly enhance energy storage density and UV–vis spectra compared to the parent HDZ system, especially in toluene. The cyano-substitutions were found to lower the highest occupied molecular orbital energy levels while raising the lowest unoccupied molecular orbital energy levels, allowing for efficient electron transfer and making these systems suitable candidates for photovoltaic applications. These findings are relevant for advancing solar energy storage technologies and photovoltaic applications. Computational modeling was performed using density functional theory (DFT) at the M062-X/6-31++G(2d,2p) and MN15/6-31++G(2d,2p) levels of theory to determine energy storage density. Time-dependent DFT (TD-DFT) was employed using CAM-B3LYP/6-31++G(2d,2p) to assess the UV–vis spectra, analyze solar spectrum matching, and evaluate the spectral overlap of the molecular structures and their photoisomers, and study their optoelectronic properties.