Zn-doped CdSSe composite quantum dots synthesized by a two-step hydrothermal ion exchange in sensitized solar cells

Abstract

Metal ion doping is an effective strategy for enhancing the photoelectric properties of quantum dots (QDs). In this study, Zn-doped CdSSe composite QDs (ZnCdSSe) were synthesized using a two-step hydrothermal ion exchange method. The synthesis process involved the exchange reaction of Cd2+ with Zn2+, followed by the exchange reaction of Se2− with S2−, based on ZnS templates. The morphology, composition and crystalline phase of synthesized QDs were characterized using X-ray and electron-based techniques such as XRD, SEM, TEM, and XPS. The results indicate ZnCdSSe QDs were synthesized while preserving a similar morphology to that of ZnCdS. Performance tests demonstrated that quantum dot sensitized solar cells (QDSSCs) equipped with ZnCdSSe/TiO2 photoanodes achieved a power conversion efficiency (PCE) of 3.61% by optimizing the hydrothermal reaction temperature and time. This efficiency was 33.2% higher than that of CdSSe (2.17%) QDSSCs synthesized via a one-step hydrothermal exchange reaction using CdS templates. The significant enhancement in PCE can be attributed to improvements in light absorption and charge carrier transport. Notably, Zn doping reduced interface charge recombination and prolong electronic lifetime (τn), facilitating more effective charge collection in QDSSCs.