Diethylenetriamine-assisted Synthesis Of Kesterite Cu₂ZnSnS₄Materials And Their Photoelectric Properties

Cu2ZnSnS4(CZTS) is the direct bandgap semiconductor materials which is consist ofearth-abundant and non-toxic elements, meanwhile, its band-gap energy is estimated to be1.50eV and its absorption coefficient is over10-4cm-1. With these intrinsic properties, CZTSis considered as one of the most suitable candidate materials for absorbing layer of thin filmsolar cells. Currently, how to synthesis CZTS materials with low-cost non-vacuum methodsbecome the research hotspot. However, in most of non-vacuum methods, toxic or expensivesolvents are employed to provide the growth environment for CZTS, it is of significance toexplore a non-vacuum synthesis method with low-cost and inexpensive solvent for CZTSmaterials.Here, we firstly successful synthesized the CZTS materials with the assistance ofnon-toxic and inexpensive solvent diethylenetriamine (DETA), and investigated theinfluences of experimental conditions on the structure and photoelectric properties of samples.The main work is as follows:(1) We synthesized pure kesterite CZTS nanoparticles by a diethylenetriamine-assistedhydrothermal method. The influences of experimental conditions (the concentration ofprecursors, the PH, the amounts of DETA) on the structure and morphology of the sampleswere investigated, the formation mechanism of CZTS and the function of DETA in thishydrothermal method were proposed. The experiment results showed that DETA isindispensable for the synthesis of CZTS in this system, and with higher concentration ofDETA, the CZTS nanoparticles with smaller size could be obtained. The FTIR and TGanalysis confirmed that DETA served as a surfactant absorbing on the surface of samples.From the calculation of UV-Vis results, the bandgap energy of sample was estimated to be1.54eV, which showed that the as-synthesized CZTS nanoparticles is suitable for theformation of ink for the preparation of CZTS film.(2) We prepared pure kesterite CZTS films by a diethylenetriamine-assisted spin-coatingmethod. The influences of precursor solution (the amount of H2O, the viscosity, theconcentration) on the structure and morphology of CZTS films were investigated. And the resistance value of CZTS films were optimized by adjusting the molar ratio of metalprecursors, the type of substrate and the vacuum sintering temperature. The results showedthat the water content and the viscosity of precursor solution have an effect on the structureand morphology of CZTS films, respectively; the substrate has impact on the crystallinity andresistance value of samples; the molar ratio of metal precursors and vacuum sinteringtemperature have great influence on the morphology and resistance value of films. Under theoptimal experimental conditions, the resistance value, thickness, absorption coefficient andbandgap of the final synthesized CZTS films are30k,2.5um,>104cm-1and1.59eV,respectively. These results indicated that the as-synthesized CZTS films have suitablephotoelectric properties that can be directly used as absorbing material for thin film solarcells.