A review of semiconductor materials as sensitizers for quantum dot-sensitized solar cells

Quantum dot-sensitized solar cells (QDSSCs) are renowned energy devices known for their distinct qualities, including (i) the ability to harvest sunlight that generates multiple electron–hole pairs, (ii) simplicity in fabrication, and (iii) low cost. The power conversion efficiency (η) rates of many QDSSCs are lower than those of dye-sensitized solar cells, reaching a maximum of 12% as a result of narrow absorption ranges and of the charge recombination occurring at the QD– and TiO2–electrolyte interfaces. New types of sensitizers are necessary to be developed to further increase the η of QDSSCs. Semiconductor QDs are the most applicable material for photosensitization because of their high absorption and the obtained emission spectra that can be manipulated by varying dot sizes. This paper presents an overview of recent studies on QDSSC photosensitization and provides suggestions to improve QDSSCs by explicitly comparing different sensitizers. Particular focus is directed on the behavior of several important types of semiconductor nanomaterials (sensitizers such as CdS, Ag2S, CdSe, CdTe, CdHgTe, InAs, and PbS) and other nanomaterials that are TiO2, ZnO, and carbon-based species. These materials are developed to enhance the electron transfer efficiency of QDSSCs. Understanding the mechanism of various photosensitization processes can provide design guidelines for future successful applications.