Structure and band gap tunable CuInS2 nanocrystal synthesized by hot-injection method with altering the dose of oleylamine

By hot-injection method with altering the dose of oleylamine (OAm) in a reaction system, CuInS 2 (CIS) nanocrystal with tunable structure and band gap is synthesized. Through various measurements, including X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), it is demonstrated experimentally that when the dose of OAm is relatively high (2.0 and 2.5   ml in this work), the combination phase of pseudo-chalcopyrite/wurtzite are obtained with a surprising existence of nanotwins. Besides, the molar fraction of wurtzite is larger in the sample using 2.5   ml OAm in the reaction system. However, when the dose of OAm becomes low, (0, 1.0 and 1.5   ml), pure zinc-blende CIS pyramidal quantum dots (QDs) can be prepared. This indicates that oleylamine promotes the formation of wurtzite structure. In addition, the band gap is larger with increasing of OAm, following the quantum refinement effects. This work serves as a facile method of synthesizing CIS nanocrystal with tunable structure and band gap, which will be possibly applied in the fabrication of their optoelectronic devices.