Enhanced photovoltage production from Canna dyes with surface passivation of ZnO based dye sensitized solar cells

Among the vast number of floras, Canna lily Red (CR) and Canna lily Yellow (CY) flower extracts were used as photosensitizers for natural dye-sensitized solar cells (NDSSC) with ZnO photoanode material. This study incorporates a blocking or compact layer (CL) below the nanoporous ZnO semiconducting metal oxide to reduce the device recombination rate. A noticeable increment of JSC after adding a compact layer is observed for both the dyes; that is for CR dye from 0.43 to 0.47 mA/cm2, and for CY dye, 0.38–0.44 mA/cm2 is obtained with a consistent high VOC of 0.54–0.60 V. Moreover, the device charge collection efficiency has been enhanced from ∼93 to ∼97% for CR dye and from ∼89 to ∼96% for CY dye-loaded films after adding a compact layer. The enhancement in JSC, VOC, and fill factor (FF) is credited to increased electron lifetime, increased diffusion length, reduced series resistance (Rs), and exclusively enhanced recombination resistance among the FTO/electrolyte interface due to the compact layer. Despite visible defect states in the ZnO photoanode, a consistent photovoltage of 0.54–0.6 V significantly manifests enhanced photovoltage production of Canna dyes in the device. The effect of compact layers on photovoltaic parameters is well established through the EIS study.