Microwave-assisted Synthesis Of Copper Zinc Tin Sulfid Nanomaterials And Its Performance Analysis

Copper zinc tin sulfide nanomaterials have been confirmed as an idealalternative for thin film solar cell absorber layer. Comparing with copper indiumselenide (CIS) or cadnium tellurium (CdTe) and copper indium gallium selenide(CIGS) semiconductors, it not only consists of earth-abundant and non-toxicelements such as In, Ga, Cd, but also exhibits a tunable direct band-gap energyranging from1.0-1.6eV and a high absorption coefficient. Meanwhile, it hassimilar electronical properties to CIGS. This paper develops a rapid synthesistechnology—microwave-assisted synthesis to fabricate Cu2ZnSnS4nanocrystals.The ionic nature and thermal stability of room temperature ionic liquids (RTIL)make them very good susceptors of MW radiation, the combination effect of anIL and MW radiation has a unique advantage for our research on the fabricationof Cu2ZnSn(SxSe1-x)4(0≤x≤1) nanocrystallines. Hence, the phase structures,morphologies and optical properties of the samples have been characterized. Thedetailed discussion is presented in this paper as follows:1. CZTS nanocrystallines have been synthesized via microwave-assisted method using oleylamine as solvent at different powers for different time period.The XRD pattern indicates that CZTS phase starts forming sooner than7min ofsynthesis time at medium fire. As the extension of time, the purity of the CZTSnanocrystals is improved, the particals are small. There can be seen that thegrain sizes and morphologies are affected by microwave power. The CZTSprepared at medium fire for13min are of the microsphere shape, the averagediameter of23.68nm and the near-optimum optical band gap of1.51eV, and thesample prepared at high fire for13min show a lath structure stacked by lots oflittle nanocrystals of10nm, and the length of the lath is~400nm, and it has aband-gap of1.5eV. At the same time, the reaction mechanism has been inferred.The process under non-vacuum conditions is simple and rapid, is property toindustrial mass production.2. Microwave-assisted RTIL method has been developed to synthesize highquality CZTS nanocrystals with ionic liquid1-n-butyl-3-methy limidazoliumtetrafluoroborate (BmimBF4) as solvent. The samples have a higher quality thanit prepared with olylamine as solvent. Research reveal that the optical propertiesand grain sizes of samples increase with heating time extension.It is found thatCZTS nanoparticles are coated with an amorphous carbon layer on their surface.The particle size is51.7±24.3nm and the band-gap is1.5eV. The experimenthas made a big progress in synthesis time with a duration of2min.3. CZTSe nanoparticles can be fabricated via microwave assisted RTILmethod using BmimBF4as solvent. The particle size of CZTSe are prepared at medium fire for2min is27.1nm and the optical band-gap is1.2eV. Furthermore, microwave assisted RTIL method has been utilized to synthesizeCu2ZnSn(SxSe1-x)4(0<x<1) nanocrystals through introducing different content ofS and Se element. The samples have been characterized by X-ray diffraction(XRD), High-resolution transmission electron microscope (TEM), Ramanspectroscope and UV-vis-NIR spectroscope. The results indicate that theintensity of Raman peak at334cm-1increased and the interplanar spacing of(112) planes corresponds to CZTSSe structure decreased with the increase of Scontents. The optical band-gap of nanocrystals range from1.2eV to1.5eV. Itcan be concluded that the prepared CZTSSe samples have tunable componentand band-gaps，which support a theoretical foundation to the made of highefficiency solar cells.