Solution-based Controllable Synthesis Of CuInS₂Nanostructures And Their Optoelectrical Characterization

Copper-based chalcogenide are a kind of important semiconductor materials whichhave been widely used in fields such as catalysis, chemical sensors, optoelectronic devices,solar cells. Here, the solution-based controllable synthesis of ternary copper-basedchalcogenide （CuInS₂） and binary copper-based chalcogenide (Cu_1.8Se, Cu_2-xSe) aswell as their applications in the field of optoelectronic devices will be researched.Specific research works are listed as follows:1. Tetragonal CuInS₂flower-like microspheres were synthesized viasolvothermal reaction in ethylene glycol （EG） using Cu（NO3）2·3H2O as coppersource, In（NO3）3·4.5H2O as indium source and thiourea as sulfur source. Theexperimental results show that pure CuInS₂were produces at the reactiontemperature200°C, which were verified to be Cu-rich by EDS, while In-rich phasewere obtained at the reaction temperature220°C. Field effect transistor （FET）based on CuInS₂flower-like microspheres obtained at200°C shows p-typeconduction. Therefore the conduction type of the as-synthesized products isexpected to be adjusted by the reaction temperature. Optical and electricalcharacterizations indicate that the band gap of the CuInS₂microspheres is about1.62eV and the conductivity is about²S cm-1, which is similar to that of theCuInS₂thin film prepared by traditional high vacuum techniques. As-synthesizedCuInS₂microspheres are expected to be used as absorb layer material in solar cellsfor the preparation of high-efficiency and low-cost CuInS₂-based photovoltaicdevices.2. Cubic Cu_1.8Se flower-like microspheres were synthesized via solvothermalreaction in ethylenediamine （en） by using elemental selenium, copper nitrate asselenium source and copper source, respectively. The experimental resultsdemonstrate that suitable surfactant PVP （0.5mmol） are needed for the synthesis ofuniform tetragonal Cu_1.8Se flower-like microspheres while the main products willbe hexagonal CuSe with excessive PVP （5mmol）. In addition, the homogeneoussolution with selenium in ethylenediamine will be beneficial to the formation ofuniform Cu_1.8Se flower-like microspheres.3. Cubic Cu_2-xSe nanowires were synthesized via hydrothermal reaction in the mixtured alkali solution of NaOH and KOH （the atomic ratio of Na/K was48.5:48.5）, selenium as selenium source, copper nitrate as copper source andhydrazine hydrate as reductant. SEM show Cu_2-xSe nanowires with length up to20μm and diameter about300-500nm. Electrical characterizations were carried out onthe Cu_2-xSe nanowire with patterned Cu electrode on one end and inert Au electrodeon the other end. I-V curves exhibit obvious electrical hysteresis phenomenon withgood reproducibility, indicating that the Cu_2-xSe nanowires have potentialapplication in nonvolatile memory.