Liu Yifan, Li Xuan, Abelian Levon, Lau Chun Hei, Min Zeyin, Hao Yuying, Dimitrov Stoichko
College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024, China.
School of Physical and Chemical Sciences, Queen Mary University of London, London E1 4NS, U.K.
ACS Omega. 2025 Feb 13;10(7):7102-7111. doi: 10.1021/acsomega.4c10169. eCollection 2025 Feb 25.
Printing perovskite films typically involves a high-temperature treatment exceeding 150 °C, which limits the manufacturing of flexible devices. All inorganic CsPbI perovskite is particularly promising for commercialization due to its high thermal stability. Herein, we discovered that when using DMF precursors containing CsI and HPbI for fabricating CsPbI films, an isopropanol (IPA) antisolvent bath immersion treatment of the wet films can enable a direct and rapid formation of optically active perovskite black phases at room temperature without annealing. In situ photoluminescence and in situ transmission techniques were employed to monitor and characterize the transition from the wet film to the final perovskite phase. It can be concluded that the relatively fast nucleation and slow grain growth during the IPA-bath treatment result in films with small grains and pronounced pinholes on the surface. Furthermore, FTIR, Raman, and NMR techniques were used to investigate changes in the chemical bonds. The characterization results revealed that the hydrogen in HPbI can form a chemical bond with the oxygen in DMF, resulting in mutual attraction. As DMF is extracted by IPA, the DMF molecule simultaneously induces the hydrogen to leave its original position, and then free cesium easily fills the vacancy left by hydrogen, forming the black-phase CsPbI perovskite. This finding reveals the mechanism of the room-temperature phase transition of CsPbI facilitated by IPA post-treatment, and it explains why the use of HPbI instead of PbI in the precursor solution effectively lowers the reaction energy barrier for CsPbI in previous works.
印刷钙钛矿薄膜通常需要超过150°C的高温处理，这限制了柔性器件的制造。全无机CsPbI钙钛矿因其高热稳定性而在商业化方面特别有前景。在此，我们发现，当使用含有CsI和HPbI的DMF前驱体来制备CsPbI薄膜时，对湿膜进行异丙醇（IPA）反溶剂浴浸泡处理能够在室温下直接快速形成具有光学活性的钙钛矿黑相，而无需退火。采用原位光致发光和原位透射技术来监测和表征从湿膜到最终钙钛矿相的转变。可以得出结论，在IPA浴处理过程中相对较快的成核和较慢的晶粒生长导致薄膜具有小晶粒且表面有明显的针孔。此外，使用傅里叶变换红外光谱（FTIR）、拉曼光谱和核磁共振（NMR）技术来研究化学键的变化。表征结果表明，HPbI中的氢可以与DMF中的氧形成化学键，从而产生相互吸引。当DMF被IPA萃取时，DMF分子同时诱导氢离开其原始位置，然后游离的铯很容易填充氢留下的空位，形成黑相CsPbI钙钛矿。这一发现揭示了IPA后处理促进CsPbI室温相变的机制，并且解释了为什么在先前的工作中在前驱体溶液中使用HPbI而不是PbI有效地降低了CsPbI的反应能垒。
