Interfacial modification of TiO₂ nanoparticles by using carbonates of earth alkali metals as an efficient and simple approach for improving quantum dot sensitized solar cell performance

In this paper, we investigate the effect of interfacial modification of TiO₂ photoelectrodes with insoluble carbonates of earth alkali metals on the suppression of electron recombination and the photovoltaic performance of the Quantum dot-sensitized solar cells (QDSSCs). This layer can form an energy barrier at the electrode/electrolyte interface that leads to a better electron injection and increases electron accumulation in the TiO₂ layer. The highest efficiency is achieved by applying TiO₂/CaCO₃/QDs layers that efficiency improves from 2.36% to 3.38% in the modified system and corresponding to 43% efficiency increment compared to bare TiO₂ based QDSSCs under standard air mass 1.5 global (AM 1.5G) simulated sun light. The higher efficiency results from an increase in the values of J_sc and V_oc, which is related to the improved electron transfer properties and decrease in the electron recombination in the QDSSCs. To find further evidence of the correlation between the effect of insulating layer and the suppression of back electron process and electron transfer rate, electrochemical impedance analyses (EIS) and the intensity modulated photocurrent/voltage spectroscopy (IMPS/IMVS) studies are performed under standard conditions. The results of this study show that this simple modification can significantly improve the performance of QDSSCs.