DFT study of polythiophene energy band gap and substitution effects

Polythiophene (pth) and its derivatives are polymer-based materials with a π-conjugation framework. pth is a useful photoelectric material and can be used in organic semiconductor devices,such as pled,oled,and solar cells. their properties are based on molecular structure; the derivatives contain different substitutes in the 3 and 5 positions,such as electron-donating or electron-withdrawing groups. all molecular geometries were optimized at b3lyp/6-31g(d,p) level of theory. the energy gap (egap) between the homo and lumo levels is related to the π-conjugation in the pth polymer backbone. in this study,the dft calculations were performed for the nonsubstituted and 3,5-substituted variants to investigate the stability geometries and electrical properties. the theoretical calculations show that the substituted forms are stable,have low egap,and are in good agreement with the experimental observations. © 2015 si. mohamed bouzzine et al.