Key Laboratory for Renewable Energy (CAS), Beijing Key Laboratory for New Energy Materials and Devices, Institute of Physics, Chinese Academy of Sciences , Beijing 100190, China.
School of Physical Sciences, University of Chinese Academy of Sciences , Beijing 100049, China.
ACS Appl Mater Interfaces. 2017 Aug 16;9(32):26937-26947. doi: 10.1021/acsami.7b08504. Epub 2017 Aug 1.
DMF as an additive has been employed in FAI/MAI/IPA (FA= CH(NH), MA = CHNH, IPA = isopropanol) solution for a two-step multicycle spin-coating method in order to prepare high-quality FAMAPbIBr perovskite films. Further investigation reveals that the existence of DMF in the FAI/MAI/IPA solution can facilitate perovskite conversion, improve the film morphology, and reduce crystal defects, thus enhancing charge-transfer efficiency. By optimization of the DMF amount and spin-coating cycles, compact, pinhole-free perovskite films are obtained. The nucleation mechanisms of perovskite films in our multicycle spin-coating process are suggested; that is, the introduction of DMF in the spin-coating FAI/MAI/IPA solution can lead to the formation of an amorphous phase PbX-AI-DMSO-DMF (X = I, Br; A = FA, MA) instead of intermediate phase (MA)PbI·2DMSO. This amorphous phase, similar to that in the one-step method, can help FAI/MAI penetrate into the PbI framework to completely convert into the perovskite. As high as 20.1% power conversion efficiency (PCE) has been achieved with a steady-state PCE of 19.1%. Our work offers a simple repeatable method to prepare high-quality perovskite films for high-performance PSCs and also help further understand the perovskite-crystallization process.
在两步多循环旋涂法中，将添加剂二甲基甲酰胺（DMF）加入到 FAIMAI/IPA（FA= CH(NH), MA = CHNH, IPA = 异丙醇）溶液中，以制备高质量的 FAMAPbIBr 钙钛矿薄膜。进一步的研究表明，DMF 的存在可以促进钙钛矿的转化，改善薄膜形貌，减少晶体缺陷，从而提高电荷转移效率。通过优化 DMF 的用量和旋涂循环次数，可以获得致密、无针孔的钙钛矿薄膜。我们的多循环旋涂工艺中钙钛矿薄膜的成核机制表明，在旋涂 FAI/MAI/IPA 溶液中引入 DMF 可以形成非晶相 PbX-AI-DMSO-DMF（X = I, Br; A = FA, MA），而不是中间相（MA）PbI·2DMSO。这种非晶相类似于一步法中的非晶相，可以帮助 FAI/MAI 渗透到 PbI 骨架中，完全转化为钙钛矿。我们的工作提供了一种简单、可重复的方法来制备高质量的钙钛矿薄膜，用于高性能 PSCs，也有助于进一步理解钙钛矿的结晶过程。该器件获得了 20.1%的功率转换效率（PCE），稳态 PCE 为 19.1%。
