Probing the Open-Circuit Voltage Improvement of DSSC via Raman Spectroscopy: In Situ Dynamic Tracking Photoanode/Electrolyte Interfaces

Photoelectric conversion efficiency is primarily determined by the carrier transport path of the dye-sensitized solar cell (DSSC) interface. While open-circuit voltage (VOC) is one of the important performance parameters in DSSCs, a deeper understanding of its correlation with the photogenerated carrier transport at the photoanode interface has always been a major challenge for researchers. Here, we propose an in situ Raman spectroscopy strategy for synchronously monitoring the VOC value of DSSCs to investigate the photoanode operation mechanisms by revealing electrolyte species and dye evolution at the photoanode/electrolyte interface. TiO2 nanoparticles are modified on TiO2 nanotube array surfaces to improve the specific surface area of dye sensitization and, thus, regulate the VOC of DSSCs. The results confirm that fluctuations in the Raman spectral intensities of polyiodide formed at the photoanode/electrolyte interface during photosensitization are highly correlated with the VOC value. Furthermore, direct spectroscopic evidence also revealed that pentaiodide is spontaneously and reversibly regenerated under DSSC operating conditions. Finally, a semiquantitative method for measuring VOC of DSSCs using Raman spectroscopy is established. This study represents that in situ Raman spectroscopy can be used as an effective platform for precisely revealing the optimization mechanism of VOC in real-time, thereby providing evidence at the molecular level for improving the photovoltaic conversion performance of DSSCs.