Efficient counter electrode for quantum dot sensitized solar cells using p-type PbS@reduced graphene oxide composite†

Abstract

This study developed a novel PbS–rGO composite counter electrode to enhance the performance of quantum dot-sensitized solar cells (QDSSCs). The composite was synthesized via a hydrothermal method by anchoring PbS nanocubes onto reduced graphene oxide (rGO) sheets. The effect of the mass ratio of rGO to PbS (0.0, 0.1, 0.3, and 0.6) on power conversion efficiency (PCE) was investigated. The optimized rGO–PbS (0.03) composite achieved a power conversion efficiency of 5.358%, V_oc of 0.540 V, J_sc of 21.157 mA cm⁻², and FF of 0.516. The rGO framework provides an interconnected conductive network that facilitates efficient charge transport, reduces charge transfer resistance, and improves overall conductivity. Electrochemical analyses confirmed the superior electrocatalytic activity of the composite in reducing the S_n²⁻/S²⁻ redox couple. The unique band alignment between rGO and PbS optimized the electron transfer pathways. The hierarchical structure increased the surface area and light absorption, enabling a more effective charge transfer at the electrode–electrolyte interface.