Single-particle spectroscopy of I–III–VI semiconductor nanocrystals: spectral diffusion and suppression of blinking by two-color excitation

Abstract

Ternary I-III-VI semiconductor nanocrystals have been explored as non-toxic alternatives to II-VI semiconductors for optoelectronic and sensing applications, but large photoluminescence spectral width and moderate brightness restrict their practical use. Here, using single-particle photoluminescence spectroscopy on nanocrystals of (AgIn)xZn2(1-x)S2 we show that the photoluminescence band is inhomogeneously broadened and that size distribution is the dominant factor in the broadening. The residual homogeneous linewidth of individual nanocrystals reaches up to 75% of the ensemble spectral width. Single nanocrystals undergo spectral diffusion which also contributes to the inhomogeneous band. Excitation with two lasers with energies above and below the bandgap reveals coexistence of two emitting donor states within one particle. Spectral diffusion in such particles is due to temporal activation and deactivation of one such state. Filling of a trap state with a lower-energy laser enables optical modulation of photoluminescence intermittency (blinking) and leads to an almost two-fold increase in brightness.

Narrow band-edge photoluminescence from AgInS2 semiconductor nanoparticles by the formation of amorphous III–VI semiconductor shells

“…These results suggest suppression of blinking, which itself is generally caused by NP charging. We indeed observed strong blinking with long off-times for the AgInS 2 /GaS x core/shell NPs synthesized by the first method ( Figure S1, supplementary information), similar to the blinking behavior of uncoated core NPs 37 . However, Figure S10 shows the time traces of PL intensity of individual core/shell NPs synthesized with the modified method before and after TOP treatment.…”

“…We next used single-particle spectroscopy to gain insight into the extent of inhomogeneity in the bandedge emission. This method has been previously used to successfully uncover the multiple-defect nature of individual ZnS-AgInS 2 solid solution NPs and to demonstrate suppression of blinking by two-color excitation 37 . In the context of the current study, the spectra of single core/shell NPs can directly answer the important question regarding whether the residual defect emission originates from the same NPs as the bend-edge emission or whether the two types of emission derive from physically distinct particles.…”

Optoelectronic Properties of Ternary I–III–VI2 Semiconductor Nanocrystals: Bright Prospects with Elusive Origins

“…It should be noted that, although we will focus primarily on CuInS 2 NCs, the following discussion is also valid for other I–III–VI 2 NCs, because very similar properties have been reported for CuInSe 2 and AgInS 2 NCs. 9,10,12,76,77…”

“…As a final remark, it should be noted that, although we focused this Perspective mostly on CuInS 2 NCs because of the wealth of data available on this material, the discussion above also applies to the less investigated members of the I–III–VI 2 NCs, because very similar properties have been reported for CuInSe 2 and AgInS 2 NCs. 9,10,12,76,77,117 It is therefore very likely that the radiative recombination mechanism is the same in all members of the I–III–VI 2 family.…”

Photophysics and electroluminescence of single nanocrystals of halide perovskites and related nanomaterials

“…Apart from the work on perovskite nanocrystals, we report on recent progress in singleparticle photophysical characterization of ternary I-III-IV semiconductor nanocrystals which have been explored as a non-toxic alternative to II-VI semiconductor quantum dots. For NCs of (AgIn)xZn2(1-x)S2 we explore the origin of defect emission, multiple emitting sites and suppression of blinking [3], and report the emergence of narrow band-edge PL in core/shell structures [4].…”