Efficient Thermally Evaporated γ‐CsPbI 3 Perovskite Solar Cells

• Published in: Advanced energy materials 2021-08, Vol.11 (29)
• Main Authors: Zhang, Zongbao, Ji, Ran, Kroll, Martin, Hofstetter, Yvonne J., Jia, Xiangkun, Becker‐Koch, David, Paulus, Fabian, Löffler, Markus, Nehm, Frederik, Leo, Karl, Vaynzof, Yana
• Format: Article
• Language: English
• ISSN: 1614-6832; 1614-6840
• DOI: 10.1002/aenm.202100299

Thin‐film deposition by thermal evaporation offers many advantages, yet in the field of perovskite photovoltaics solution‐processed devices significantly outperform those fabricated by thermal evaporation. Here, high‐quality γ‐CsPbI 3 perovskite layers by coevaporation of PbI 2 and CsI with a small amount of phenylethylammonium iodide (PEAI) are deposited. It is demonstrated that the addition of PEAI into the perovskite layers leads to a preferred crystal orientation and a far improved microstructure, with columnar domains that protrude throughout the film's thickness. This is accompanied by a reduced density of defects as evidenced by the increase in photoluminescence and decrease in Urbach energy as compared to reference CsPbI 3 films. Photovoltaic devices based on the PEAI containing perovskite layers reach up to 15% in power conversion efficiency, thus surpassing not only the performance of reference CsPbI 3 devices, but also that of most solution‐processed PEAI containing inorganic CsPbX 3 (X = Cl, Br, I) perovskite solar cells. Importantly, encapsulated thermally evaporated perovskite devices maintain their performance for over 215 days, demonstrating the stabilizing effect of PEAI on thermally evaporated CsPbI 3 .