Tailoring defects of CuInS2 quantum dots for sensitized solar cells

Abstract

Owing to composition and corresponding defect states, the optical and electronic properties of quantum dots (QDs) have a major impact on the performance of quantum dot sensitized solar cells (QDSCs). A series of CuInS2 QDs with intentionally introduced defects from Cu-deficiency were synthesized under air circumstance by the organometallic high temperature method. Feature of tunable photoluminescence of CuInS2 QDs with long lifetime has been demonstrated, which was mainly attributed to the donor-acceptor pair recombination, contributed above 70% to the whole emission profiles. The rate constants of electron transfer (ket) from CuInS2 QDs to TiO2 varied from 0.09 × 1010 s−1 to 1.48 × 1010 s−1, depending on the compositions of the QDs. CuInS2 QDSCs exhibited power conversion efficiency of 5.71% under one full sun illumination. The improved photovoltaic performance of CuInS2 QDSCs is mainly originated from broadened optoelectronic response range up to ∼950 nm, and fast electron injection from QDs to TiO2 films, which provide strong photoresponse beyond 60% over the window below 700 nm. The synthetic approach combined with defects created by composition modulation introduces a new approach towards the goal of high performance QDSCs.