金属盐硫脲水溶液的稳定性及其对Cu_2ZnSn(S,Se)_4薄膜形成、结构和性能的影响

Stability of Metal/Thiourea Aqueous/Ethanol-based Precursor Solution and its Effect on Formation,Structure and Properties of Cu_2ZnSn(S,Se)_4 Thin Film

分别以氯化铜(CuCl_2·H)_2O)、氯化锌(ZnCl_2)、氯化亚锡(SnCl_2·2H)_2O)和硫脲为Cu、Zn、Sn和S源,以去离子水和少量乙醇混合溶液为溶解液,配制出用于制备单一锌黄锡矿结构Cu_2ZnSnS_4(W-CZTS)薄膜的前驱体溶液.研究发现这种前驱体溶液由于化学不稳定会产生沉淀,导致制备的薄膜不是由单一W-CZTS相,而是由W-CZTS和其他杂相组成,且晶体质量很差;当把少量的巯基丙酸(MPA)加入到前驱体溶液中后,不仅可以提高前驱体溶液的化学稳定性、避免沉淀发生,而且利用加入MPA前驱体溶液及旋涂和硒化技术还可以制备出高致密、大晶粒、单一锌黄锡矿结构的Cu_2ZnSn(S,Se)_4薄膜(W-CZTSSe).以所制备的W-CZTSSe薄膜为吸收层,获得光电转换效率为7.25%的CZTSSe基太阳能电池.此外,还系统研究了前驱体溶液不稳定和MPA提高其稳定性的化学机制.研究表明,在这种前驱体溶液加入少量MPA的方法是一种环境友好型的制备高致密、大晶粒、单一W-CZTSSe薄膜的有效方法.

In the present work,a metal/thiourea aqueous/ethanol-based precursor solution used for fabricating a single phase of Cu2 Zn Sn S4（ CZTS） thin film with kesterite structure was prepared by using CuCl2·H）2O,ZnCl2 SnCl2·2H）2O and thiourea as Cu,Zn,Sn and S sources,respectively,and mixture solution of deionized water and ethanol as solvent. It is found that the precursor solution is unstable and easily produce a mass of precipitation,leading to that the thin film prepared by using it is not composed of a single phase of kesterite CZTS and has poor crystal quality. However,the stability of the precursor solution can be improved greatly by adding a small amount of 3-mercaptopropionic acid（ MPA） into the solution,avoiding any precipitation. And a single phase of kesterite Cu2 Zn Sn（ S,Se）4（ CZTSSe） thin film with large grain size and hole-free was prepared by using the precursor solution added the MPA as well as spinning-coating and selenization techniques. Using the CZTSSe film as absorb layer,we fabricated CZTSSe-based solar cell with a power conversion efficiency of7. 25%. It is also suggested that chemical mechanisms of the unstability of the precursor solution and improvement of the stability by addition of the MPA into the precursor solution. The present work demonstrated that the solution approach of addition of MPA into the precursor solution is effective method of preparation of a single phase of CZTSSe film with kesterite structure,large grain size and hole free.