Molecular engineering of xanthene dyes and graphene oxide-TiO2 nanocomposite for high-performance dye-sensitized solar cells applications

Herein, we present a comprehensive theoretical investigation of a series of six metal-free xanthene dyes to uncover their photovoltaic parameters and electron injection characteristics for high performance dye-sensitized solar cells (DSSCs) applications. Both Density functional theory (DFT) as well as time-dependent DFT calculations were carried out to understand how structure of xanthene dyes effects the overall photovoltaic properties and hence device performance against graphene oxide@TiO 2 (GO@TiO 2 ) as semiconductor ​. Here we note that while xanthene dyes and graphene oxide nanohybrid are incapable of offering solar cell characteristics but coupling of graphene oxide with TiO 2 i.e. GO@TiO 2 nanocomposite provides robust photovoltaic characteristics. Elaborate assessment of the simulated results indicates that among the dye series Eosin B and Y offer the lowest band gap competent with decorous quality of light absorption characteristics covering the whole UV and visible wide range of the sun irradiation empowering highest light harvesting capacity (0.860), open circuit voltage (1.75 V), free energy of electron injection (-1.52 eV) compared to other dyes. Furthermore, xanthene dyes have low reorganization energy and xanthene@GO@TiO 2 composite offers highest charge separation. Moreover, Eosin B and Y provide high LUMO level density confirming highest interaction with the semiconductor. These findings are crucial for providing guidelines for device modelling involving xanthene based highly efficient DSSCs.