多步旋涂过程中CsPbBr_(3)无机钙钛矿成膜机理  

Formation mechanism of CsPbBr_(3) in multi-step spin-coating process

作　　者：马书鹏 林飞宇 罗媛 朱刘 郭学益 杨英[1,2,3] Ma Shu-Peng;Lin Fei-Yu;Luo Yuan;Zhu Liu;Guo Xue-Yi;Yang Ying(School of Metallurgy and Environment,Central South University,Changsha 410083,China;Hunan Key Laboratory of Nonferrous Metal Resources Recycling,Central South University,Changsha 410083,China;National&Regional Joint Engineering Research Center of Nonferrous Metal Resources Recycling,Changsha 410083,China;Guangdong Provincial Enterprise Key Laboratory of High Performance Thin Film Solar Materials,Qingyuan 511517,China;First Materials Co.,Ltd.,Qingyuan 511517,China)

机构地区：[1]中南大学冶金与环境学院,长沙410083 [2]中南大学,有色金属资源循环利用湖南省重点实验室,长沙410083 [3]有色金属资源循环利用湖南省工程研究中心,长沙410083 [4]广东省高性能薄膜太阳能材料企业重点实验室,清远511517 [5]清远先导材料有限公司,清远511517

出　　处：《物理学报》2022年第15期272-280,共9页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:61774169);清远市创新创业团队项目(批准号:2018001);广东省科技计划(批准号:2018B030323010);中南大学研究生自主探索创新项目(批准号:2021zzts0612)资助的课题。

摘　　要：在无机钙钛矿太阳能电池的研究中,薄膜制备工艺是影响钙钛矿太阳能电池光电转换效率(PCE)的重要因素之一.CsPbBr_(3)钙钛矿作为稳定性极好的无机钙钛矿之一,因其前驱体盐(PbBr_(2),CsBr)溶解度差异过大,通常采用多步法进行制备.而由于对成膜机理的认识不充分,导致制备的薄膜存在薄膜形貌差、前驱体反应不完全等问题.本文通过旋涂不同次数的CsBr溶液,探究了CsPbBr_(3)钙钛矿的成膜机理.成膜过程中CsBr扩散进入预先沉积的PbBr_(2)薄膜完成反应,短暂反应时间使薄膜深层反应不充分而薄膜表面过度反应,CsPb_(2)Br_(5)和Cs_(4)PbBr_(6)等相伴随CsPbBr_(3)钙钛矿出现,反复退火形成的薄膜阻挡CsBr扩散加剧了这一现象.适当地延长前驱体的反应时间,能为CsBr扩散及反应提供更充分的空间.基于优化反应时间,CsPbBr_(3)钙钛矿薄膜形貌得到改善、其晶粒尺寸得到提升,钙钛矿薄膜中的晶界减少,从而抑制了载流子复合.在4次旋涂和30 s反应时间的条件下,组装的CsPbBr_(3)钙钛矿太阳能电池开路电压从1.01 V提升至1.28 V,PCE从5.32%提升至6.30%,器件短路电流密度J_(sc)=8.40 mA/cm^(2),填充因子FF=59%.基于以上研究,为多步旋涂法制备CsPbBr_(3)钙钛矿薄膜和电池提供了理论借鉴.The quality of perovskite films plays a crucial role in solar cell,which can affect the stability and power conversion efficiency(PCE).As one of inorganic perovskites with excellent stability,CsPbBr_(3) perovskite is usually prepared by multi-step method due to the large difference in solubility between its precursor salts(PbBr_(2) and CsBr).The main reason is that the formation mechanism of CsPbBr_(3) film is not thoroughly studied.The incomplete reaction of PbBr_(2) and emergence of Cs_(4)PbBr_(6) when the CsBr is excessive become problems that need to be solved urgently.In this paper,the phase transition of films during spin coating is observed in detail.In the process of film formation,the CsBr diffuses into the predeposited PbBr_(2) film to complete the reaction.The short reaction time results in insufficient reactions inside the film but overreaction on the surface of film.The CsPb_(2)Br_(5) and Cs_(4)PbBr_(6) appear with CsPbBr_(3) perovskite,and the film formed by repetitively annealing blocks the diffusion of CsBr.Methanol has an etching effect on the perovskite film which can eliminate the blocking effect.By extending the reaction time of CsBr solution on the film surface,the PbBr_(2) in the bottom layer is fully reacted,and after being annealed,the perovskite film will recrystallize to form a compact film.With the reaction time controlled appropriately,the CsPb_(2)Br_(5) in the film can be effectively reduced and Cs_(4)PbBr_(6) will not appear.The film grain size increases,grain boundary decreases,and the recombination is effectively inhibited,which ensures the improvement of the photoelectric performance of the solar cell.Under the condition of spin-coating four times and reaction time of 30 s,the solar cell has 6.30%PCE,Voc = 1.28 V,Jsc = 8.40 mA/cm~2,FF = 0.59.Comparing with the solar cells with no extended reaction time,the PCE improves more than 18%.This work will provide an important insight into the growth mechanism of perovskite film toward high crystallinity and less defects.

关 键 词：无机钙钛矿 CsPbBr_(3) 多步旋涂法 反应机理 反应时间 

分 类 号：TM914.4[电气工程—电力电子与电力传动]