A rational design of excellent light-absorbing dyes with different N-substituents at the phenothiazine for high efficiency solar cells

Dye-sensitized solar cells (DSSCs) have attracted great interest due to their simple fabrication process and low cost. However, most organic dyes with D-p-A configuration usually exhibit narrow absorption band, leading to poor light harvesting ability and great loss on photon conversion efficiency. In this research, a series of excellent light-absorbing dyes (CC202-I - CC202-III) with different N-substituents at phenothiazine entities based on the champion dye CC202 were designed and investigated by density functional theory (DFT) and time-dependent DFT (TD- DFT). According to the analysis of absorption property, the results demonstrated that different Nsubstituents (12-crown-4-substituted phenyl, 4-hexoxyphenyl, and bare phenyl) at phenothiazine entities lead to stronger and broader absorption band aswell as red-shifted spectra; moreover, larger electronic injection driving force (Delta G(inject)), regeneration driving force (Delta G(reg)), capability of light harvested (eta(LHE)(lambda(strong))/(eta) over bar (LHE) (lambda)) and maximal photon generated current (J(ph)) in CC202-I - CC202-III are observed compared to that of CC202, which further increase JSC. Additionally, a larger VOC can be obtained in CC202-I - CC202-III due to larger dipole moment (unormal) and slow electron recombination rate. Considering the all calculated characteristics related to JSC and VOC, dyes with 12-crown-4-substituted phenyl, 4-hexoxyphenyl, and bare phenyl substituent on phenothiazine can effectively enhance the photoelectric conversion efficiency of DSSCs. (C) 2020 Published by Elsevier B.V.