Kebede Tamiru, Abebe Mulualem, Mani Dhakshnamoorthy, Paduvilan Jibin Keloth, Thottathi Lishin, Thankappan Aparna, Thomas Sabu, Kamangar Sarfaraz, Shaik Abdul Saddique, Badruddin Irfan Anjum, Aga Fekadu Gochole, Kim Jung Yong
Faculty of Materials Science and Engineering, Jimma Institute of Technology, Jimma University, Jimma P.O. Box 378, Ethiopia.
Department of Physics, College of Natural and Computational Science, Bonga University, Bonga P.O. Box 334, Ethiopia.
Micromachines (Basel). 2023 Aug 14;14(8):1601. doi: 10.3390/mi14081601.
The phase change of all-inorganic cesium lead halide (CsPbI) thin film from yellow δ-phase to black γ-/α-phase has been a topic of interest in the perovskite optoelectronics field. Here, the main focus is how to secure a black perovskite phase by avoiding a yellow one. In this work, we fabricated a self-doped CsPbI thin film by incorporating an excess cesium iodide (CsI) into the perovskite precursor solution. Then, we studied the effect of organic additive such as 1,8-diiodooctane (DIO), 1-chloronaphthalene (CN), and 1,8-octanedithiol (ODT) on the optical, structural, and morphological properties. Specifically, for elucidating the binary additive-solvent solution thermodynamics, we employed the Flory-Huggins theory based on the oligomer level of additives' molar mass. Resultantly, we found that the miscibility of additive-solvent displaying an upper critical solution temperature (UCST) behavior is in the sequence CN:DMF > ODT:DMF > DIO:DMF, the trends of which could be similarly applied to DMSO. Finally, the self-doping strategy with additive engineering should help fabricate a black γ-phase perovskite although the mixed phases of δ-CsPbI, γ-CsPbI, and CsPbI were observed under ambient conditions. However, the results may provide insight for the stability of metastable γ-phase CsPbI at room temperature.
全无机铯铅卤化物（CsPbI）薄膜从黄色δ相转变为黑色γ-/α相一直是钙钛矿光电子领域的一个研究热点。在此，主要关注点是如何通过避免出现黄色相来确保获得黑色钙钛矿相。在这项工作中，我们通过在钙钛矿前驱体溶液中加入过量的碘化铯（CsI）制备了一种自掺杂的CsPbI薄膜。然后，我们研究了有机添加剂如1,8 - 二碘辛烷（DIO）、1 - 氯萘（CN）和1,8 - 辛二硫醇（ODT）对其光学、结构和形态性质的影响。具体而言，为了阐明二元添加剂 - 溶剂溶液的热力学性质，我们基于添加剂摩尔质量的低聚物水平采用了弗洛里 - 哈金斯理论。结果发现，显示出上临界溶液温度（UCST）行为的添加剂 - 溶剂的混溶性顺序为CN:DMF > ODT:DMF > DIO:DMF，其趋势同样适用于二甲基亚砜（DMSO）。最后，尽管在环境条件下观察到δ - CsPbI、γ - CsPbI和CsPbI的混合相，但通过添加剂工程的自掺杂策略应该有助于制备黑色γ相钙钛矿。然而，这些结果可能为亚稳γ相CsPbI在室温下的稳定性提供见解。
