Phase Behavior and Role of Organic Additives for Self-Doped CsPbI3 Perovskite Semiconductor Thin Films

Tamiru Kebede; Mulualem Abebe; Dhakshnamoorthy Mani; Jibin Keloth Paduvilan; Lishin Thottathi; Aparna Thankappan; Sabu Thomas; Sarfaraz Kamangar; Abdul Saddique Shaik; Irfan Anjum Badruddin; Fekadu Gochole Aga; Jung Yong Kim

doi:10.3390/mi14081601

Phase Behavior and Role of Organic Additives for Self-Doped CsPbI₃ Perovskite Semiconductor Thin Films

Micromachines (Basel). 2023 Aug 14;14(8):1601. doi: 10.3390/mi14081601.

Authors

Affiliations

¹ Faculty of Materials Science and Engineering, Jimma Institute of Technology, Jimma University, Jimma P.O. Box 378, Ethiopia.
² Department of Physics, College of Natural and Computational Science, Bonga University, Bonga P.O. Box 334, Ethiopia.
³ School of Chemical Sciences, Mahatma Gandhi University, Kottayam 686560, India.
⁴ Department of Physics and Mathematics, Università Cattolica del Sacro Cuore, Via della Garzetta, 48, 25133 Brescia, BS, Italy.
⁵ Department of Physics, Baselius College, Kottayam 686001, India.
⁶ School of Energy Materials, Mahatma Gandhi University, Kottayam 686560, India.
⁷ Mechanical Engineering Department, College of Engineering, King Khalid University, Abha 61421, Saudi Arabia.
⁸ Department of Materials Science and Engineering, Adama Science and Technology University, Adama P.O. Box 1888, Ethiopia.
⁹ Center of Advanced Materials Science and Engineering, Adama Science and Technology University, Adama P.O. Box 1888, Ethiopia.

Abstract

The phase change of all-inorganic cesium lead halide (CsPbI₃) 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 CsPbI₃ 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-CsPbI₃, γ-CsPbI₃, and Cs₄PbI₆ were observed under ambient conditions. However, the results may provide insight for the stability of metastable γ-phase CsPbI₃ at room temperature.

Keywords: black γ-phase; cesium lead iodide; organic additive; perovskite; phase behavior; self-doped; yellow δ-phase.

Grants and funding

The authors extend their appreciation to the Deanship of Scientific Research at King Khalid University for funding this work through Large Group Research Project under grant number RGP.2/201/44.