The Synthesis Of Micro-nano CZTS Absorbing Layer And Study On Their Optoelectronic Properties

Abstract:Cu2ZnSnS4(CZTS) is a kind of P-type semiconductor material with a direct band gap, which has the prominent advantages, such as suitable band gap(-1.5eV) which matches well with the best band gap that required by the semiconductor solar cells, high absorption coefficient up to10-4cm-1, and elements contained in CZTS are abundant and non-toxic and has little pollution to the environment. Thus, CZTS has been considered as one of the best candidate material used as the absorption layer of solar cell materials. In this paper, CZTS micropaticles have been successfully synthesized by a liquid reflux method under normal pressure and temperature, the chemical pure metal chlorides and precipitated sulfur are chosen as raw materials, and organic solvent TETA is priority selected as the reaction solvent during the synthesis process, then the influence factors are deeply discussed. With the incorporation of Se element, CZTSe micropowders with controllable morphology and tunable band gap were obtained. Providing a new approach to prepare high quality CZTS powders with high efficiency and low cost. The results indicate that among the four solvents used in the initial stage, CZTS powder can be obtained only when the TETA was chosen as the reaction solvent. The as-obtained products are considered to be CZTS with pure phase、stoichiometric composition and uniform morphology, the band gap is determined to be1.5eV. With the increase of the reaction temperature, it is conducive to obtain CZTS with pure phase^good crystallinity、stoichiometric composition and uniform morphology, However, when the reaction temperature increased to250degree, the temperature has already become very close to the boiling temperature of the TETA, considering that the boiling temperature of the TETA is determined to be266-267degree, so the temperature is not suitable to be further increased. The as-obtained products have a small band gap which is not conducive for the photoelectric conversion when the reaction rime is relatively short. After the reaction time reached4h, the band gap of the as-prepared tends to be stable at about1.5eV which is suitable for the preparation of CZTS absorbing layer for high efficiency solar cells. The addition of surfactant will accelerate the speed of reactions. With the incorporation of the Se element, CZTSe powder with controllable morphology were obtained. With the increase of the ratio of Se, the microstructure of the as-prepared product will be gradually turned from granular to sphere-like. and the surface of the as-prepared product presents sheet-like structure. The band gap of the CZTSe decreased gradually with the constantly incorporation of Se element.