Design of novel phenanthrocarbazole dyes for efficient applications in dye-sensitized solar cells

Abstract

Phenanthrocarbazole (PC)-based organic dye-sensitized solar cells (DSSCs) have been recently reported in experiments with an impressive high power conversion efficiency of over 12%. In this paper we report a computational study of the electronic structures, optical parameters and electron injection properties of a series of five PC dyes and the dye-TiO2 interfaces. Density functional theory (DFT) and time-dependent DFT (TDDFT) approaches were employed. We show that the incorporation of additional building blocks (indoline, carbazole, triphenylamine, or coumarin) to the PC donor moiety leads to obvious influence on the electronic structures and properties, compared to unitary electron donor PC dye. The binary electron-donor PC based dyes demonstrate better electronic properties and spectroscopic parameters. The calculated injection time of electrons from the excited state of dye to the conduction band of TiO2 is ideal for DSSC applications. The newly designed coumarin-PC and indoline-PC dyes show desirable energetic, electronic, and spectroscopic parameters for DSSCs. Our results are useful for a better understanding on the design rule of PC based organic dyes for future DSSCs.