Sol-gel CdS layer for TiO₂ nanorod-based quantum dots-sensitized solar cells

Abstract The CdS layer was essential for CdSe quantum dot-sensitized solar cells (QDSSCs) as the seed layer and energy barrier. Here, a novel sol–gel method was employed to prepare the CdS interlayer (SG-CdS) for TiO₂ nanorod-based QDSSCs. Due to the sufficient reaction of the Cd and S sources in the sol–gel solution, SG-CdS exhibited fewer impurities than CdS produced by commonly used chemical bath deposition (CBD-CdS). QDSSCs with SG-CdS exhibited an open-circuit voltage of 490 mV, a short-circuit current density of 14.12 mA cm⁻², and a fill factor of 0.35. The power conversion efficiency of the QDSSCs with SG-CdS was 2.48%, which was higher than that of the QDSSCs with CBD-CdS (2.02%). Moreover, electrochemical impedance spectroscopy showed that the QDSSCs with SG-CdS yielded a charge recombination resistance of 99.92 Ω at a bias voltage of −0.5 V, demonstrating less charge recombination than the QDSSCs with CBD-CdS (82.16 Ω). Therefore, the performance of the CdSe QDSSCs could be improved by reducing the impurities in CdS. This study revealed the advantages of SG-CdS in replacing CBD-CdS as the interlayer for charge transport, as well as good applicability with nanorod photoanodes in QDSSCs.