Density functional theory calculations of photophysical properties of linear 2, 7-carbazole derivatives as solar cell materials

Abstract

A theoretical study has been performed to explore the optical and electronic properties on a series of linear 2, 7-carbazole derivative (PCDTBT) by introducing vinyl (v) as linkage and/or benzene (B) as end-capped group for solar cell materials. The PBE0/6-31G(d) method was employed to calculate the frontier molecular orbital (FMO) and energy gap of all derivatives. The values of energy gap change less than 0.28 eV depending on v as linkage and/or B as end-capped group. The absorption spectra was evaluated using the TD-PBE0/6-31 + G(d,p) level on the basis of the optimized geometries. The absorption spectrum has a red shift along with the increasing of molecular chain. The results of ionization potential (IP), electron affinity (EA), and reorganization energy (λ) reveal that, v as linkage and/or B as end-capped group both lead to the increase of charger transfer rates for PCDTBT. Moreover, v as linkage and/or B as end-capped group have slight effects on the stability property of PCDTBT.

Keywords:

• density functional theory calculations
• photophysical and charge transport property
• stability property
• 2, 7-carbazole derivatives
• solar cells

Acknowledgements

The authors thank the Science and Technology Research Projects for Education Department of Jilin Province (No. 201130). Natural Science Foundation of Jilin Province (No. 201215180).