DFT/TD-DFT calculations of the electronic and optical properties of bis-N,N-dimethylaniline-based dyes for use in dye-sensitized solar cells

Using density functional theory (DFT) and time-dependent DFT (TD-DFT) methods, the current study reports the role of inserting acyclic and cyclic conjugated pi-linkers in bis-N,N-dimethylaniline-based dyes as sensitizers in the dye-sensitized solar cells (DSSCs). Some optical and electron transfer parameters are calculated to accomplish our objective. The results show that increasing number of ethylene pi-linker (-CH=CH-) enhances light harvesting efficiency but decreases the driving force for electron injection and possibility of dye regeneration with encouraging dye aggregation on the surface of the electrode. Extending the conjugation length of the linker decreases the efficiency, while incorporating some cyclic conjugated linkers has a positive effect on the efficiency through effective coexistence of both direct and indirect mechanisms of electron injection. A comparison with experiment and previous theoretical studies on NKX-2554 (P1) and NKX-2569 (P2) is considered.