A theoretical investigation of the optoelectronic performance of some new carbazole dyes

Density functional theory and time-dependent approaches are applied for theoretical investigation of a new class of novel carbazole-based d-D-pi-A-type dyes, where the carbazole moiety is the main electron donor, bithiophene behaves as a pi-bridge, and cyanoacetic acid as an electron acceptor for all the studied dyes, whereas the terminal electron donor unit is varied to thiophene, thienothiophene, carbazole, dimethoxyphenyl, and indole. The influence of the terminal electron donor on the optoelectronics properties is investigated for the dyes in isolated state and in chloroform solvent. Their absorption spectra and electronic and structural properties are evaluated and discussed. The theoretical results show that all the dyes exhibit excellent optoelectronic properties. In particular, D5 with indole as the terminal electron donor moiety has potential for use as a sensitizer for nanocrystalline TiO2 solar cells based on its red-shifted absorption spectrum, reduced energy gap, lowest lambda(total) value, and higher Delta G(Reg) values.