We report on the photoluminescence (PL) mechanisms and the nature of the related electronic states of AgInS2 quantum dots (QDs) synthesized via a metathesis reaction of metal complexes. A broad PL band with a large Stokes shift is apparent in the PL spectra of AgInS2 QDs whose average diameter is 2.6 nm. The characteristic decay behavior of the PL spectra and the peak shift of the PL band depending on the excitation intensity indicate that the PL is attributed to the donor−acceptor (DA) pair recombination. The binding energies of the donor and acceptor are estimated to be 100 and 220 meV. These values are derived from the temperature dependence of the PL intensity and an analysis of the spectral profile of the PL spectrum considering the DA pair recombination processes. Furthermore, we show that the phonon sidebands constitute the dominant contribution to the PL spectra because of the strong electron−phonon interaction of carriers trapped by these donors or acceptors.

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We report on mechanisms of highly fluorescent donor− acceptor pair emissions in chalcopyrite AgInS 2 quantum dots (QDs). We observed that photoluminescence quantum yields (PL-QYs) and radiative recombination rates strongly depend on the QD size; smaller QDs exhibit higher PL-QYs and higher radiative recombination rates of up to 60% and 10 6 s −1 , respectively. Such characteristics were examined in terms of concentrations of donors and acceptors estimated from PL decay behaviors analyzed by the theory of Thomas and Hopfield. These analyses revealed that concentrations of donors and acceptors are higher for smaller QDs; this significantly enhances radiative recombination rates and PL-QYs in smaller QDs. In turn, higher concentrations of donors and acceptors in smaller QDs can be attributed to the use of lower synthesis temperatures, which increase the population of donor−acceptor-type lattice defects.

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