Polyoxometalate-modified ternary copper-tungsten-sulfide nanocrystals as high-performance counter electrode materials for quantum dots-sensitized solar cells

The Cu2WS4/[Me2NH2]11[CeIII(PW11O39)2] (CWS/CeIII(PW11)2) composite is synthesized by simple sol-vothermal method and first applied as a counter electrode material in CdS/CdSe/ZnS-sensitized quantum dot sensitized solar cell (QDSSCs). Due to the co-existence of copper and tungsten in different valence states, the ternary CWS has more redox active sites than the binary Cu2S. Besides, the conduction band of CeIII(PW11)2 and CWS are well matched, so the electrons transport from CB of CeIII(PW11)2 to CWS is a favorable exothermic process. Brunauer-Emmett-Teller (BET), electrochemical impedance spectroscopy (EIS), Tafel-polarization test (Tafel), open-circuit voltage decay (OCVD) and cyclic voltammetry (CV) tests all confirmed that 4% CeIII(PW11)2/CWS (CWS-4) has the highest electrocatalytic activity. Under simulated sunlight, QDSSCs with CWS-4 CE delivered a power conversion efficiency (PCE) of 6.63% (Jsc = 23.42 mA cm-2, Voc = 0.62 V, FF = 0.46), which is 12% and 44% higher than QDSSCs with CWS and Cu2S CEs, respectively. CeIII(PW11)2, as an electron-transport mediator to compound with CWS can generate shallow electron traps, increase active sites, and effectively inhibit the recombination of charges, thereby enhancing cell performance.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

The Cu2WS4/[Me2NH2]11[CeIII(PW11O39)2] (CWS/CeIII(PW11)2) composite was synthesized and used as a counter electrode material in CdS/CdSe/ZnS-sensitized quantum dot sensitized solar cell (QDSSCs). The CWS has more redox active sites than Cu2S due to the co-existence of copper and tungsten in different valence states. The CWS-4 CE showed the highest electrocatalytic activity and improved cell performance by generating shallow electron traps and inhibiting charge recombination.