Unusual Spectral Diffusion of Single CuInS2 Quantum Dots Sheds Light on the Mechanism of Radiative Decay

The luminescence of CuInS 2 quantum dots (QDs) is slower and spectrally broader than that of many other types of QDs. The origin of this anomalous behavior is still under debate. Single-QD experiments could help settle this debate, but studies by different groups have yielded conflicting results. Here, we study the photophysics of single core-only CuInS 2 and core/shell CuInS 2 /CdS QDs. Both types of single QDs exhibit broad PL spectra with fluctuating peak position and single-exponential photoluminescence decay with a slow but fluctuating lifetime. Spectral diffusion of CuInS 2 -based QDs is qualitatively and quantitatively different from CdSe-based QDs. The differences reflect the dipole moment of the CuInS 2 excited state and hole localization on a preferred site in the QD. Our results unravel the highly dynamic photophysics of CuInS 2 QDs and highlight the power of the analysis of single-QD property fluctuations.