Preparation And Photoelectric Properties Study Of Morphology Controllable Cu₂ZnSnS₄Nanomaterials

At present, CIGS has become one of the most successful materials currently being commercializedfor thin-film photovoltaic devices, and the current power conversion efficiencies of CIGS based solar cellshave been pushed beyond20%. However, indium and gallium used for preparation of the active layers arerare and expensive, which would inhibit a cost-effective large scale production. Cu₂ZnSnS₄（CZTS） is aquaternary semiconductor with high absorption coefficient in the visible region (over10⁴cm^-1) and theband gap about1.4-1.6eV, which is very close to the optimum value for being used as an absorbed layer insolar cells. Moreover, it is nontoxic, and the elements it contained are abundant in the crust in comparisonwith those of CIGS. Owing to these special properties, CZTS is considered to be a promising material forapplication in low cost and environmentally friendly thin film solar cells. In this paper, we successfullyprepared hierarchical CZTS particles with different morphologies and dimensions via the facilesolvothermal method, and the mechanism of crystal growth of the typical flowerlike particles are discussedand analyzed in detail. In addition, the photoelectric properties of the final products have also beeninvestigated, which indicate that this hierarchical nanostructure with special advantages has potential use inphotovoltaic devices. This thesis includes the following main aspects:1. The CZTS particles have been successfully prepared with different solvents （ethylenediamine （En）,ethylene glycol （EG） and polyethylene glycol-400（PEG）） via the convenient solvothermal method, and thestructure and morphologies of as-prepared particles were characterized by XRD, TEM, SEM, EDS and soon. The results showed that sperelike and flowerlike CZTS particles can be synthesized by EG with PVP assurfactant and single PEG （PEG and EG）. In addition, the different reaction conditions （temperature,solution concentration, the amount of PVP and reaction time） were also investigated, which showed that230oC is the best temperature to synthesis CZTS particles, the size and morphology of the CZTS particlescan be controlled by changing the reaction conditions, and PVP played an important role in the formationof the final hierarchical particles. The UV-vis spectra indicated that the absorption of typical hierarchicalCZTS particles decayed more slowly, indicating a higher absorption coefficient in the visible region incomparison with spherelike CZTS particles and CZTS nanocrystals.2. The photoelectric properties of the CZTS particles have been discussed, the CZTS-FTO films were prepared by the simple blade coating method, and then the films were annealed in the furnace, which wereused as absorbed layer and counter electrode, respectively. The better photoelectric conversion efficiency（3.99%） was obtained when CZTS-FTO film （flowerlike particles） was used as counter electrode incomparison with Pt electrode （3.91%）. In brief, all the results indicated that the flowerlike CZTS particleswith hierarchical structures are expected to be used as both absorbed layer and counter electrode materialsin solar cells.