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Drastic influence of substituent position on orientation of 2D layers enables efficient and stable 3D/2D perovskite solar cells

2023    Gunes, Ummugulsum; Yaylali, Figen Varlioglu; Karabag, Zeynep Gozukara; Gao, Xiao-Xin; Syzgantseva, Olga A.; Karabag, Aliekber; Yildirim, Gulsevim Bensu; Tsoi, Konstantin; Shibayama, Naoyuki; Kanda, Hiroyuki; Rafieh, Alwani Imanah; Zhong, Liping; Zuttel, Andreas; Dyson, Paul Joseph; Yerci, Selcuk; Nazeeruddin, Mohammad Khaja; Gunbas, Gorkem

The lack of long-term stability and reproducibility of perovskite solar cells (PSCs) is the main roadblock preventing their successful commercialization. 3D/2D PSCs are one of the most prominent ways to address these issues. Various salts that are mostly based on phenyl ethyl ammonium iodide (PEAI) have been utilized to grow a 2D perovskite layer on 3D perovskites. Herein, we report the effect of substituting the methoxy (-OMe) group at the ortho (o), meta (m), and para (p) positions on PEAI salts. Photoluminescence and time-resolved photoluminescence show that o-OMe-PEAI-treated surfaces achieve reduced defect densities and nonradiative recombination rates compared with the other analogs. Devices with PCEs over 23% are achieved for o-OMe-PEAI-based 3D/2D PSCs, and the enhanced performance is attributed to the favorable formation energy and desired vertical orientation according to the density functional theory (DFT) analyses. Finally, the unique orientation of the o-OMe-PEAI-based 2D perovskite results in significantly enhanced long-term, moisture, and thermal stability.