Solid-State Succinonitrile/Sulfide Hole Transport Layer and Carbon Fabric Counter Electrode for a Quantum Dot Solar Cell

A solid-state quantum dot solar cell (QDSC) is implemented with cadmium sulfide (CdS) quantum dots (QDs) tethered to titanium oxide (TiO2) as photoanode, carbon fabric (C-fabric) as counter electrode (CE), and a solid electrolyte of succinonitrile/Na2S mixed in a 2:1 molar ratio (SN/S2–) as the hole transport material. Electron transfer and recombination processes are investigated by intensity-modulated photocurrent spectroscopy (IMPS) and intensity-modulated photovoltage spectroscopy (IMVS) for a TiO2/CdS/ZnS-SN/S2–-C-fabric (solid state) and TiO2/CdS/ZnS-S2–-C-fabric (liquid junction) devices at different white light intensities. IMPS and IMVS studies show that the electron transport rate and electron recombination decrease with an increase in the intensity of light. The champion cell with a TiO2/CdS/ZnS photoanode and C-fabric as CE delivers a power conversion efficiency (PCE) of 5.2% with a solid electrolyte of SN/S2–, and a PCE of 6.3% is obtained with the liquid aqueous electrolyte of 0.1 M Na2S. The effects of temperature on solar cell performance and the thermal dependence of ionic conductivity for the solid electrolyte are studied in detail. This study shows that the succinonitrile based solid electrolyte is a good substitute for the traditional liquid electrolyte.