Effects of NH₄F concentrations of electrolytes and reaction time in the anodic oxidation process on the photovoltaic properties of back-illuminated DSSC

This study develops photoelectrode thin film needed in back-illuminated dye-sensitized solar cells (DSSC) by the anodization method. We test the effects of electrolytes with different NH4F concentrations reaction time lengths in the anodic oxidation process on the photoelectric conversion efficiency of DSSC, and measure the open-circuit voltage decay, lifetime of electrons and incident photontoelectron conversion efficiency (IPCE) of the prepared DSSC. Experimental results show that the TiO₂ nanotube thin film prepared by anodic oxidation with an electrolyte with a NH4F concentration at 0.75 wt% and with a reaction time of 5 hr achieves a photoelectric conversion efficiency of 3.98%, open-circuit voltage of 0.723 V, and short-circuit current density of 11.3 mA/cm², and has a longer electron lifetime when compared to the electrolytes prepared at other NH4F concentrations. In addition, the photoelectrode thin film prepared with a thickness of 22 μm under a reaction time of 10 hr and by an electrolyte with a NH4F concentration at 0.5 wt% achieves photoelectric conversion efficiency of as high as 4.76%, open-circuit voltage of 0.681 V, and short-circuit current density of 15.91 mA/cm².