Photoluminescence of CuInS 2 nanocrystals: effect of surface modification

Abstract

We have synthesized highly luminescent Cu-In-S(CIS) nanocrystals (NCs) by heating the mixture of metal carboxylates and alkylthiol under inert atmosphere. We modified the surface of CIS NCs with zinc carboxylate and subsequent injection of alkylthiol. As a result of the surface modification, highly luminescent CIS@ZnS core/shell nanocrystals were synthesized. The luminescence quantum yield (QY) of best CIS@ZnS NCs was above 50%, which is 10 times higher than the initial QY of CIS NCs before surface modification (QY=3%). Detailed study on the luminescence mechanism implies that etching of the surface of NCs by dissociated carboxylate group (CH3COO-) and formation of epitaxial shell by Zn with sulfur from alkylthiol efficiently removed the surface defects which are known to be major non-radiative recombination sites in semiconductor nanocrystals. In this study, we developed a novel surface modification route for monodispersed highly luminescent Cu-In-S NCs with less toxic and highly stable precursors. Investigation with the timeand the temperature-dependent photoluminescence showed that the trap related emission was minimized by surface modification and the donor-acceptor pair recombination was enhanced by controlling copper stoichiometry.

Synthesis and Characterization of Green Zn–Ag–In–S and Red Zn–Cu–In–S Quantum Dots for Ultrahigh Color Quality of Down-Converted White LEDs

“…It was reported that the blue shift of the alloying process is attributable to the formation of solid solutions with wider band gaps of ZnS, to the surface etching of I−III−VI QD during the shell growth and, consequently, to the reduction of effective core QD size. 46,47 Here, the variations of the peak wavelength, fwhm, QY, and CIE color coordinates of the green ZAIS and red ZCIS QDs are displayed as a function of the shelling, alloying, or both reaction step of the ternary AIS or CIS cores and ZnS (Figure 1e−h). The peak wavelengths of the last alloyed green ZAIS and red ZCIS QDs reached 501 and 606 nm with fwhm values of 81 and 106 nm, respectively.…”

Radiative and Nonradiative Recombination in CuInS2 Nanocrystals and CuInS2-Based Core/Shell Nanocrystals

“…1,9,14−17 To date, the best results have been reported for CIS/CdS core/shell NCs, which show PL QYs up to 86%, 9,14 while for CIS/ZnS core/shell NCs, PL QYs up to 70% have been reported. 14,18 Alternative strategies to obtain high PL QY CIS-based core/shell NCs employing exclusively cadmium-free materials are desired but have not yet been devised. In fact, while in the well-known lead and cadmium chalcogenide NCs (e.g., PbSe and CdSe) the PL originates from radiative recombination of a delocalized electron in the conduction band (CB) with a delocalized hole in the valence band (VB), the origin of PL in CIS NCs is still under debate.…”

Fractional Contributions of Defect‐Originated Photoluminescence from CuInS2/ZnS Coreshells for Hybrid White LEDs

“…It indicates the broad spectral contribution from the interface-trapped state and defect-related DA-trapped state to the PL of CIS/ZnS. However, the broad PLE shoulder disappeared or was reduced for CIS/ZnS 665 nm which implies that the wide size distribution and various types of defect play a role in the further spectral broadening of PLE [16]. The absorption and PLE spectra of CIS/ZnS did not exhibit the multiple distinct peaks which could be observed from the II-VI SNCs with sizes near the bulk Bohr radius as a result of quantum confinement [17].…”