Beneficial Intrinsic Hole Trapping and Its Amplitude Variation in a Highly Photoluminescent Toxic-Metal-Free Quantum Dot

Abstract

Intrinsic hole trapping as well as hole detrapping have not been observed for any quantum dot (QD) or perovskite nanocrystal (PNC) system. Moreover, amplitude variation of intrinsic hole trapping (or detrapping) has not been reported at all for any QD or PNC system. However, for a CuInS2-based core/alloy-shell (CAS) QD system, (a) both intrinsic hole trapping and detrapping have been observed and (b) very significant amplitude variations of hole trapping (∼16 to ∼42%) and hole detrapping (∼44 to 23%) have been observed. Unlike detrimental electron trapping, hole trapping has been shown to be beneficial, having a direct correlation toward increasing PLQY to 96%. Simultaneous electron and hole trapping has been shown to be quite beneficial for the CuInS2-based CAS QD system leading to the longest ON time (∼130 s) for which a nontoxic metal-based QD remains only in the ON-state without blinking.

Transforming exciton dynamics in perovskite nanocrystal through Mn doping

“…The higher peak value of the distributions of ON fraction for PNC1 in comparison to PNC2 corroborates well with the higher PLQY of the host band for PNC1. 8,10,11,28–35 These SPS-based observations point to the fact that because of Mn doping (the host band of) PNC2 spends more time in the OFF state in comparison to undoped PNC, i.e. PNC1.…”

Advancements in semiconductor quantum dots: expanding frontiers in optoelectronics, analytical sensing, biomedicine, and catalysis

“…8A). [66][67][68][69][70][71][72][73] Photoluminescence excitation (PLE) measurements were used to reveal excitation energydependent (EED) PLQYs, which were first shown by Hoheisel et al 66 These measurements showed a monotonic drop in CdSe NC PLQY when ensembles were stimulated to the blue of their band edge. The reason for this decrease is explained as particles being excited into a range of states that differed from constrained NC states.…”

“…71 Nonetheless, it has been discovered that sometimes hole trapping can be beneficial for increasing the PLQY for CuInS 2 -based core/alloy-shell CQDs while maintaining the same EED PLQY trend. 72 Regarding EED PLQYs, there is conflicting evidence suggesting that they might be artifacts resulting from measurement mistakes. According to Tonti et al, EED PLQYs are caused by excess surface ligands and NC aggregates in the solution.…”

Direct Synthesis and Characterization of Hydrophilic Cu-Deficient Copper Indium Sulfide Quantum Dots

“…PLQY of core–shell CIS QDs can be as high as 80–96%. , However, in contrast to the narrow emission profiles of band edge emitting materials such as CdSe, CIS QDs exhibit a large Stokes shift and a relatively broad emission band, suggesting a significant contribution from intraband defect recombination pathways. ,,, In addition, for larger CIS nanoparticles approaching the Bohr exciton radius, the long wavelength side of the photoluminescence (PL) spectral peak extends further than that allowed by a band edge transition in the bulk material. Furthermore, the PLQY of Cu-deficient CIS QDs, with their associated high density of copper vacancy defects, is greater than that of an equivalent stoichiometric sample, , indicating that defects play a significant role in CIS QD emission.…”