Theoretical insight into electronic structure and optoelectronic properties of heteroleptic Cu(I)-based complexes for dye-sensitized solar cells

A series of heteroleptic Cu(I)-based dyes were investigated by density functional theory (DFT) and time dependent DFT (TD-DFT). Results showed that Cu(I)-based dyes were inclined to form distorted pseudotrigonal pyramidal configurations with four-coordinated geometry index tau(4) ranging from 0.905 to 0.914. The absorption spectra of Cu(I)-based dyes covered similar to 300.0-600.0 nm region, and the lowest excitation states were crucial for efficient electron excitation and separation. Suitable energy levels of Cu(I)-based dyes rendered them thermodynamically favorable for efficient electron injection into semiconductor and regeneration from electrolyte. Relative to pi-conjugation, heteroaromatic groups introduced into ancillary ligands could significantly improve the property of Cu(I)-based dyes by decreasing HOMO-LUMO gaps, red-shifting spectral range, strengthening absorption intensity, boosting light-harvesting efficiency, and promoting interfacial electron injection. Specifically, Cu(I)-based dye with dithiole-functionalized group exhibited outstanding optoelectronic property. (C) 2016 Elsevier B.V. All rights reserved.