Hysteresis analysis in dye-sensitized solar cell based on different metal alkali cations in the electrolyte

Hysteresis phenomenon occurs in solar cells and its cause is still an arguable issue as it redefines how accurately we control the device performance. Here, the hysteresis behavior in Dye-sensitized solar cell (DSSC) is studied based on the electrolyte. Three electrolytes were used containing Sodium iodide (NaI), Potassium iodide (KI), and Cesium iodide (CsI). Current density-voltage characteristics was measured for each device at fast (1 V/s) scan rate, medium (0.5 V/s) scan rate, and slow (0.1 V/s) scan rate. The charging-discharging process at TiO2/electrolyte interface during forward and reverse scan directions is propose as the responsible mechanism for hysteresis in DSSC. Based on our investigation, hysteresis phenomenon is strongly dependent on the size of alkali metal cation as well as J-V sweep scan rate. Hysteresis is dominant for NaI electrolyte with the smallest Na+ cation size while it diminishes for KI and CsI electrolytes with bigger K+ and Cs+ sizes, respectively. Also, using CsI electrolyte along with the slow scan rate of 0.1 V/s is the perfect combination for the minimal hysteresis in the solar cell. In addition, hysteresis index calculation was redefined based on the intercept cross points between forward and reverse scan directions. Our results suggest that DSSC has a charge storage efficiency accompanied by its primary function as a power conversion device. The charge storage ability occurs for V > VOC during the forward scan and it is significant for smaller cation size.