High entropy oxides (CuCoMnMgZn)O microspheres as counter electrodes for quantum dot sensitized solar cells

Abstract

In quantum dot sensitized solar cells (QDSSCs), the counter electrode serves as an essential component by collecting electrons from the external circuit and catalyzing the electrolyte. In this work, four spinel-type high-entropy oxides are synthesized using a solvothermal method and are being applied with CdTe/Mn-CdS/CdSe/ZnS photoanodes for QDSSCs to explore counter electrode materials with better performance by adjusting the elements in the high-entropy oxides. The exploration reveals that the surface of (CuCoMnMgZn)O appears rough, with pores and a large specific surface area (125.61 m²/g), supplying substantial active sites to promote electron transfer and facilitate electrolyte access. The counter electrode photovoltaic conversion efficiency (PCE) of QDSSCs composed using this material is 8.33 %, which is significantly higher than that of other high entropy oxides (6.5–7.5 %). Other photovoltaic performances are demonstrated as J_sc = 26.25 mA· cm⁻², V_oc = 0.646 V, and FF = 0.49. Electrochemical impedance spectroscopy (EIS) and continuous cyclic voltammetry curves confirm the lowest charge transfer resistance (R_ct = 0.191 Ω) and good stability in the S²⁻/S_n²⁻ reduction reaction. Both the higher catalytic activity and stability further indicate that the high-entropy oxide could be a prospective material for QDSSCs counter electrodes.