Charge generation and transfer performance enhancement of size-balanced CuInS2 quantum dots sensitized solar cells

The optical absorption and charge dynamics of different sized CuInS2 quantum dots have been investigated. Exact sizes from 2.5 to 4.1 nm of CuInS2 quantum dots are prepared and further deposited on the TiO2 films. The optical absorption property of CuInS2 quantum dots sensitized photo-electrodes are analyzed by UV–Vis spectra, which provides electron generation property of the photo-electrodes. And the electron–hole separation property of the photo-electrodes is characterized by photoluminescence spectra with different size of quantum dots. The electrochemical impedance spectra and time-resolved photoluminescence decay are employed to measure the charge dynamics, which indicates that better electron transfer property can be obtained by the small size of quantum dots. With the balance of charge generation and charge transfer performance, 3.6 nm sized CuInS2 QDs sensitized photo-electrodes achieves excellent photovoltaic performance.