Study On Polylol Solution Chemical Synthsis Of Cu-In-Ga-Se System Nanocrystals

This paper gives an overview of development and classfication of solar cells,preparation of the related thin films, and properities and modification research ofCu-In-Ga-Se system nanocrystals. The preparation of Cu-In-Ga-Se systemnanocrystals by hot solvent method is researched. We use copper chloride, indiumchloride, gallium chloride and selenium powder as precursor sources. The propertiesof the Cu-In-Ga-Se system nanocrystals are characterized through changing differentpolyhydric alcohol solvents, reducing agent, selenium source, reaction temperaturesand reducing agent injection temperatures. The results show that using diethyleneglycol as solvent to prepare CIGS nanocrystals is better. So in this paper, we prepareCuInSe₂, CuIn_0.75Ga_0.25Se₂, CuIn_0.50Ga_0.50Se₂and CuGaSe₂nanocrystals in diethyleneglycol system by a green new method—hot solvent method. By studying on changingof reaction temperature, amount of reducing agent and PVP, refluxing reaction time,this paper analyzes mechanism of preparation of nanocrystals by hot solvent method.The structure, morphology, chemical composition and optical performance ofCuIn_0.75Ga_0.25Se₂nanocrystals are characterized by analysis of X-raydiffraction（XRD）, field emission scanning electron microscopy（FESEM）, highresolution transmission electron microscopy （HRTEM）, ultraviolet-visiblespectrophotometer （UV-Vis）. The results show that particle size of CuInSe₂,CuIn_0.75Ga_0.25Se₂, CuIn_0.50Ga_0.50Se₂and CuGaSe₂nanocrystals prepared at210℃for20min are19.8nm,17.0nm,15.6nm and14.9nm, respectively, their band gap are1.01eV，1.20eV，1.40eV and1.68eV, respectively.Cu-In-Ga-Se system nanocrystals were prepared in diethylene glycol system in theexperiment. The experimental results show that nanocrystals obtained in diethyleneglycol system have better performance. Cu-In-Ga-Se system nanocrystals havesmall agglomeration when not adding surfactants. After PVP is added, the result hasremarkably improvement. However, with increasing of amount of PVP, carbonizationmay happen in the process of heat treatment, which has side effects on theperformance of films, so how to choose appropriate dispersant needs to be studied inthe future. We also find that injection temperature of reducing agent have certaineffect on stoichiometric ratio of nanocrystals. The reaction temperature significantly improves the rate of crystal nucleation and growth, the optimal synthesizedtemperature of Cu-In-Ga-Se system nanocrystals is210℃, because when thetemperature is too low, the reaction is not complete and there exists a large number ofelemental selenium. The crystallinity of nanocrystals is better with increasing ofreaction time. In addition, diethylene glycol has coordinating ability with nanocrystalsparticles, which has good effects on dispersion of nanocrystals and stability ofcolloids.