Theoretical investigation of the influence of different electric field directions and strengths on a POM-based dye for dye-sensitized solar cells

Abstract

An inner electric field generated between the electrode and the counter electrode when DSSCs work has an inevitable effect on the conversion efficiency, and it is important to reveal the influence of the electric field direction and strength on the performance of DSSCs. Theoretical calculations based on density functional theory (DFT) and time-dependent DFT (TD-DFT) were employed to analyze the electronic structures, optical properties and electron transfer processes under on-field and off-field conditions. The interfacial electron transfer (IET) processes across the semiconductor interface were evaluated, which have been less investigated previously. Compared to the off-field condition, the conversion efficiency of DSSCs is increased when the electric field acted on the +X axis due to the broader absorption spectra, larger ICT parameters, and larger short-circuit photocurrent density governed by the injection driving force. In addition, the further increased conversion efficiency with increased electric field strength indicates that the POM-based dye has self-promoting properties, meaning that the generated inner electric field increases the light harvesting properties of the POM-based-dye, which in turn forms stronger electric field strengths, and finally improves the performance of DSSCs. It is expected that the present study could establish the relationship between the electric field and DSSC efficiency.