Computational Study on the Interaction of Iodide Electrolyte/Dye/TiO2 Interface in Dye-Sensitized Solar Cells

Abstract

Dye-sensitized solar cells (DSSCs) represent an emerging and promising candidate as a future renewable energy resource because of their potential low-cost fabrication cost, environmentally friendly, stability, and efficient solar energy conversion1. However, the intrinsic dye/iodide interaction with the dye on the semiconductor surface in understanding the DSSCs mechanism remains unclear2.In this work, three metal-free organic dyes based on D–π–A architecture were designed and computationally investigated for understanding the DSSCs mechanism and improving its efficiency2 - 4. The different donor groups were employed for the comparative study noted as D1Y, D2Y, and D3Y. This computational study mainly aims at determining the effect of the interaction of the iodide/triiodide with the dye on the semiconductor surface using the first-principles calculations (see scheme.1). We investigated the structural and electronic properties of these dyes when standing alone and being adsorbed on the oxide surface with the iodide electrolyte. Our studies revealed that the incorporation of a strong donor unit in D1Y and D 2 Y dyes in combination with iodide electrolytes on the TiO2 surface provides better adsorption and electronic properties in comparison to those from the dye alone on the TiO2 surface. Analysis of density of states (DOS) revealed that the dye with a strong electron-donating group, mainly D1Y and D2Y with an iodide electrolyte on the surface remarkably upshifts the Fermi energy, thereby improving the efficiency of the DSSCs by increasing the open-circuit voltage (Voc). These current findings provide a valuable hint for attaining a deeper understanding of the intrinsic interaction taking place at the electrolyte/dye/TiO2 interface. References O’Regan, B.; Grätzel, M.A Low-Cost High-Efficiency Solar Cell Based on Dye-Sensitized Colloidal TiO2 Films. Nature 1991, 353, 737– 740.Hailu, M. and J.-C. Jiang Phys. Chem. Chem. Phys., 2020, 22, 26410-26418.Hailu, W.-R. Shie, S. Nachimuthu and J.-C. Jiang, ACS Sustain. Chem. Eng., 2017, 5, 8619-8629.Hailu, M. T. Nguyen and J.-C. Jiang, Phys. Chem. Chem. Phys., 2018, 20, 23564-23577. Figure 1