Unveiling the temperature-dependent optoelectronic performance of acrylonitrile derivatives for organic semiconductors: A comprehensive DFT and experimental analysis

This study investigates the optoelectronic properties, crystal structures, and thermodynamic behaviors of two newly synthesized hydroxy-substituted phenylacrylonitrile derivatives (3a and 3b), starting from their synthesis. Experimental findings demonstrate that compound 3a exhibits superior optical semiconductor potential, particularly due to its lower band gap values. To better understand the mechanisms responsible for this superiority, the thermodynamic properties of the molecules-including heat capacity, entropy, enthalpy, and total energy-were systematically calculated using Density Functional Theory (DFT) at room temperature and over a temperature range. While the relationship between molecular dynamics and non-radiative decay is acknowledged in the literature, the quantitative impact of temperature-dependent thermodynamic parameters on the optoelectronic performance of organic semiconductors, as well as the mechanisms behind this effect, remains insufficiently explored. This research addresses this gap by demonstrating that the lower heat capacity, enthalpy, and entropy values of compound 3a, in comparison to 3b, are directly associated with reduced molecular dynamism and consequently enhanced optical efficiency. Linking electronic structure to thermodynamic rigidity reveals that reduced vibrational freedom in compound 3a extends exciton lifetimes, illuminating temperaturedependent decay pathways and highlighting its promise as a flexible optoelectronic active layer.