Effect of Ga ion doping in the ZnS passivation layer for high-efficiency quantum dot-sensitized solar cells

Highlights: • The Ga³⁺ is introduced into the ZnS passivation of QDSSCs by SILAR approach smoothly. • The Zn-Cu-In-Se QDs are prepared by high-temperature hot-injection method typically. • The PCE of QDSSCs using ZCISe/Ga-ZnS QDs as sensitizers reaches 8.72% remarkably. -- Abstract: The recombination of carriers at the photoanode-electrolyte interface is one of the crucial factors hindering the improvement of the photoelectric property of quantum dot-sensitized solar cells (QDSSCs). Passivation layers such as ZnS have been often used to suppress this charge loss, but the effect still needs to be improved. In this paper, Ga³⁺ is introduced into the traditional ZnS passivation of QDSSCs via a successive ion layer adsorption and reaction (SILAR) approach to further improve the photovoltaic performance. The power conversion efficiency (PCE) of QDSSCs using Zn-Cu-In-Se/Ga-ZnS QDs as sensitizers reaches 8.72%, significantly higher than the 7.7% of Zn-Cu-In-Se/ZnS QDs, demonstrating that the incorporation of Ga³⁺ in the ZnS layer can optimize the solar absorption and effectively reduce the appearance of carrier recombination, providing a novel means for QDSSCs optimization.