Nanocluster seed-mediated synthesis of CuInS2 quantum dots, nanodisks, nanorods, and doped Zn-CuInGaS2 quantum dots

摘要

Recent work using seed-mediated quantum dot growth has shown that nanoparticle seeds are a useful method for providing nucleation centers in order to control the nanoparticle shape and composition. Here we present a facile nanocluster seed-mediated protocol to synthesize CuInS2 quantum dots (q-dots) and Zn and/or Ga doped CuInS2 (Zn-CuInGaS2) q-dots using (NH4)(2)S as a sulfur source. Due to high reactivity of (NH4)2S toward metal cations, we are able to isolate a CuInS2 nanocluster (< 2 nm with low crystallinity) intermediate at low temperatures (60 degrees C). By varying the conditions of a "heat-up" synthesis method, these nanoclusters can be grown into CuInS2 with different morphologies (q-dots, nanodisks, and nanorods) and different crystalline phases (chalcopyrite and wurtzite). Further, we can incorporate dopant Ga3+ and Zn2+ ions into the q-dots by introducing the dopant either during the nanocluster formation or during the crystal growth stage, resulting in CuInGaS2 and CuInZnS q-dots. Incorporation of both Ga and Zn increases the photoluminescence intensity compared to CuInS2; furthermore, the absorption spectra and photoluminescent emission peaks are shifted to shorter wavelengths. With this nanocluster method, we have also synthesized pentanary Zn-CuInGaS2 for the first time. Compared to quaternary CuInGaS2 and CuInZnS, we observe a larger blue shift in the absorption spectra when both Zn and Ga are present. The interesting optical properties of Zn-CuInGaS2 makes it an attractive material for photovoltaic devices and light emitting diodes. The ability to isolate the intermediate CuInS2 nanoclusters provides a strategy for synthesizing a wide variety of tailored quaternary and pentanary metal chalcogenides in the future.