Photocarrier recombination dynamics in ternary chalcogenide CuInS₂ quantum dots

Abstract

Photocarrier recombination dynamics in ternary chalcogenide CuInS2 quantum dots (CIS QDs) was studied by means of femtosecond transient-absorption (TA) and nanosecond time-resolved photoluminescence (PL) spectroscopy. Under strong excitation, the TA dynamics in CIS QDs is well described by a simple rate equation including single-carrier trapping, free-to-bound recombination, and trap-assisted Auger recombination. Under weak excitation, on the other hand, the PL decays of the QDs are composed of a short-lived component caused by surface trapping and a long-lived one caused by free-to-bound recombination. It is found that the surface trapping accelerates markedly with decreasing QD size while the free-to-bound radiative recombination hardly depends on the QD size. Besides this, we observed both a decrease in the PL lifetimes and a dynamic spectral redshift, which are attributed to the surface trapping and the coexistent inhomogeneous broadening in CIS QDs. The spectral redshift becomes less pronounced in CIS/ZnS core/shell QDs because of the suppression of the fast nonradiative recombination caused by the passivation of the surface traps. These results give clear evidence that the free-to-bound model is appropriate for interpreting the optical properties of CIS QDs.

Photoluminescence Enhancement of CuInS2 Quantum Dots in Solution Coupled to Plasmonic Gold Nanocup Array

“…Compared to the typical lifetime of tens of ns for CdSe QDs, the PL lifetime of CIS QDs is much longer with an amplitude‐weighted averaged lifetime around 200 ns. Such a long lifetime and multi‐exponential decay behavior have been reported in previous research . The excited‐state dynamics for this type of QDs is still under debate and not clearly understood yet, mainly due to uncertainties in the ternary CIS QD composition, size and shape, and external/internal defects.…”

“…The excited‐state dynamics for this type of QDs is still under debate and not clearly understood yet, mainly due to uncertainties in the ternary CIS QD composition, size and shape, and external/internal defects. Some initial studies have attributed the short lifetime components to surface or interface defect states and the longer components to intrinsic defect states possibly involving donor–acceptor recombination transitions . Recent studies have suggested that the short lifetime components are related to the band edge surface trapping and/or defect‐induced charge recombination, while the longer one was attributed to subbandgap transition between band edge electrons and Cu vacancy localized holes …”

Interplay of bimolecular and Auger recombination in photoexcited carrier dynamics in silicon nanocrystal/silicon dioxide superlattices

“…The most feasible possibility is three-particle Auger recombination when one carrier is trapped 9 , 12 , 29 . This would require a presence of traps within a silicon band gap.…”

Strong Dependence of Quantum-Dot Delayed Luminescence on Excitation Pulse Width

“…Auger processes have been largely overlooked in nanocrystal photophysics, and only relatively recently has their significance gained recognition. [16][17][18] The inset to Figure 4E shows the same curves normalized to their plateau magnitudes. Again, the curvature shows very little power dependence, consistent with experiment.…”