The band bending effect of LiI/NaI treated TiO2 photoanodes on the performance of dye-sensitized solar cells

Abstract

A new method has been developed for surface treatment of TiO₂ photoanodes with LiI/NaI to enhance the photocurrent and, subsequently, the performance efficiency of the fabricated dye-sensitized solar cells (DSSCs). Three different concentrations (0.1, 0.25, and 0.5 mmol%) of LiI and NaI solutions were used to investigate the effect of this surface treatment on the device performance of DSSCs. A positive shift in the energy level of TiO₂ has been experienced by surface treated devices, which is predominantly supported by the decrease in V_OC. Furthermore, the introduction of LiI/NaI onto the TiO₂ surface resulted in a reduction in the crystallite size, indicating an increase in the surface area which helps in more dye adsorption leading to higher J_SC values of the devices. Besides, modification of the conduction band energy level, it also allows a fast electron injection process by shifting the density of states. Thus, this approach offers a simple but efficient route to enhance the photocurrent and efficiency of DSSCs.