Optimization of performance and stability of quantum dot sensitized solar cells by manipulating the electrical properties of different metal sulfide counter electrodes

Abstract

Fabrication of low cost and high catalytic active counter electrode (CE) for quantum dot sensitized solar cells is one of the dynamic ways to enhance the performance of quantum dot solar cell. In this investigation, different CE materials such as copper sulfide (Cu2S), cobalt sulfide (CoS) and nickel sulfide (NiS) were deposited on fluorine doped tinoxide (FTO) glass and brass plate by single step electrophoretic deposition technique and solar cell performance and stability of three different CEs were tested. Electrochemical deposition parameters were optimized for the optimization of CEs performance. Electrical properties of Cu2S, CoS and NiS CEs were investigated by electrochemical impedance spectroscopy and electrical properties were compared with the observed solar cell performances and stability. Of the tested CEs materials, enhanced solar cell performance was observed with Cu2S CE than the CoS or NiS CEs while brass substrae was found to be a better substrate than FTO for these CE materials. The optimized Cu2S/brass plate CE showed current density of (Jsc) 17.9mA.cm−2, open circuit voltage of (Voc) 494.5mV, fill factor of (FF) 59.0% and efficiency of 5.2% with the solar cell fabricated with PbS/CdS q-dot anode. While Cu2S/FTO glass plate CE showed Jsc of 16.1mA.cm−2, Voc of 489.4mV, FF of 52.9% and efficiency of 4.2% of with the same q-dot anode. A higher electrocatalytic activity together with the lower charge transfer resistance (Rct) and good inter-connected Cu2S particles on brass electrodes were found to be the major CE properties that decides the performance of CE.