Synergestic effect of chlorophyll and anthocyanin Co-sensitizers in TiO2-based dye-sensitized solar cells

Abstract

We adopted co-sensitization technique for improvement of photovoltaic performance of dye-sensitized solar cells (DSSC). Three natural dyes were used in the fabrication of DSSCs: chlorophyll dyes from Talinum fruticosum (waterleaf) labeled as A, Telfairia Occidentalis (pumpkin leaf) labeled as B and anthocyanin dye from the Caesalpinia Pulcherrima (pride of Barbados) flower labeled as C. Then, the DSSCs-based blended dyes were fabricated at volume percent of 25:75, 50:50 and 75:25 for respective AB, AC and BC mixed dyes. The solar cells were evaluated using UV–Vis spectroscopy, electrochemical impedance spectroscopy (EIS) and current-voltage (I-V) characteristics. The results show that DSSC, from single dyes, fabricated from C has the best PCE of 0.25% while mixed dye (BC) at 25:75% volume yielded the best PCE of 1.14% with an open-circuit voltage (Voc) of 0.64 V, short-circuit current density (Jsc) of 2.91 mA/cm2 and fill factor (FF) of 61% under standard (AM 1.5 G) 1 sun illumination (100 mW/cm2). Generally, cells fabricated from BC (for all volume %) outperformed both single and other mixed DSSCs. The EIS measurement revealed the existence of low and high charge transfer resistances in BC-25:75% and AB-25:75%, respectively at the photoanode and electrolyte interface. Also, continuous light soaking test on the optimized device (BC-25:75%) showed that 11% of the device's power conversion efficiency (PCE) was lost after 7 h. This indicates that co-sensitization of dyes of different sources could be a very promising and effective strategy for further improvement for natural DSSCs.