Unusual Spectral Diffusion of Single CuInS(2) Quantum Dots Sheds Light on the Mechanism of Radiative Decay

[Image: see text] 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.