Size dependent photoelectrochemical performance of eco-friendly CuInS2 quantum dots

Colloidal quantum dots (QDs) are considered as new energy materials with great potential, especially environmentally friendly QDs that do not contain heavy metals. Compared with heavy metal QDs, non-toxic QDs still suffer low performance in photovoltaic (PV) as well as photoelectrochemical (PEC) applications. The fabrication of high-performance PV devices from environmentally friendly QDs has become the focus of researchers. Before moving to experiments, the theoretical aspect is a very good way to deeply understand the charge carrier dynamics inside the QDs, which can provide possible solutions to improve the PEC performance of the QDs based photoelectrodes. Here, we report the successful synthesis of eco-friendly CuInS2(CIS) QDs with variable particle size. Through time-domain PL spectroscopy, we found that the photoluminescence (PL) lifetime gradually decreased from 273.2 ns to 172.9 ns as the size of CIS QDs increased. By theoretical calculations we also studied the dynamics of electrons and holes. The theoretical studies revealed that as the size of CIS QDs increases, the wave functions of the overlap between the electron and impurity hole increases leading to the decreased PL lifetime.