Microwave-Assisted Hydrothermal Synthesis of CuS Nanoplate Films on Conductive Substrates as Efficient Counter Electrodes for Liquid-Junction Quantum Dot-Sensitized Solar Cells

CuS nanoplate films were synthesized on FTO conducting glass substrates via a facile microwave-assisted hydrothermal (MHT) route and applied directly as a low-cost and high-efficiency counter electrode (CE) for liquid-junction quantum dot-sensitized solar cells (QDSSC). The two-dimensional structure of nanoplate provide high surface area for more active catalytic sites and easy accessibility for polysulfide electrolyte, which leads to the remarkable decrease in charge transfer resistance and the enhancement of catalytic activity of CE. As a result, the liquid-junction QDSSC assembled with the prepared CuS-2 CE achieves maximum power conversion efficiency (PCE) of 4.97%, which is superior than that of CuS fabricated by conventional chemical bath deposition method based cell (PCE 4.06%) and the 100 nm thin sputtered Pt/FTO CE based cell (PCE 3.08%). Furthermore, the prepared CuS exhibits highly chemical stability in polysulfide electrolyte, resulting in reproducible performance. These results show the potential application of MHT synthetic method in preparing metal chalcogenide CE for high-performance liquid-junction QDSSC in the future.