Tunable optical properties of ternary non‐stoichiometric Cu–In–S nanocrystal emitters

Abstract

Low toxic, non-stoichiometric colloidal copper–indium–sulphur [Cu–In–S (CIS)] ternary quantum dots with different Cu:In molar ratios by a hot-injection method in octadecene was synthesised. The Cu:In precursor molar ratios were 1/10, 1/20 and 1/40. Varying the fraction of cationic and capping agents, the compositions of CIS nanocrystals were precisely controlled. The photoluminescence (PL) results reveal that, reducing the Cu:In ratio in the CIS is the feasible strategy for bandgap engineering. Tunable PL emissions have been observed. X-ray powder diffraction and high-resolution transmission electron microscopy results indicate that as-prepared CIS nanocrystals are compositional homogeneity. The single-crystal nature of CIS nanocrystals improves the relative PL quantum yield up to 12%, which exhibits substantial enhancement comparing with the stoichiometric CuInS2 and CIS-based semiconductor core QDs. The PL decay curve of CIS has a triexponential feature. The value of τ 1, τ 2 and τ 3 of CIS sample agree well with CuInS2 core QDs. The average PL lifetime of CIS is reduced to 146.9 ns, which can be attributed to the reduction of surface-related trap states.