Studying the role of ZnO nanostructure photoanodes for improving the photovoltaic performance of CdSe QDSSCs

The photoanode is one of the principal components in QDSSCs and its organization has an incredible influence on the cell performance. Here we report the investigations on the influence of photoanode material based on ZnO nanodot, nanorod, nanoplate, and nanoflower on the performance of CdSe quantum dot-sensitized solar cells. For the QDSSCs fabrication, a well-dispersed aqueous solution of 5 nm sized CdSe quantum was synthesized using the chemical method, and the working electrode was dipped for 10 h for adsorption of photosensitizer on ZnO nanostructures. The performance of the photoanode is further improved by surface modification of quantum dot by the introduction of a ZnS buffer layer using the SILAR method. The ZnS buffer layer on the surface of the CdSe quantum dot decreases the backscattering of charge carriers. The optimized number of SILAR cycles for maximum device efficiency was estimated for each photoanode cells. The obtained efficiencies were found to increase from 0.50 to 0.92% (4th cycle), 1.55% (3rd cycle), 2.69% (3rd cycle), and 3.05% (2nd cycle) for the ZnO nanodot, nanorod, nanoplate, and nanoflower-based CdSe QDSSCs, respectively. Better conversion efficiency was noticed for cells fabricated with ZnO nanoflower as photoanode using a minimum number of SILAR cycles. Improved photon scattering, multiple reflections, light harvesting, and higher electron lifetime lead to the enhancement of device performance. The results give an insight into the efficiency improvement strategies for QDSSCs with ZnO nanostructure-based photoanode.