Drastic influence of substituent position on orientation of 2D layers enables efficient and stable 3D/2D perovskite solar cells
Ummugulsum Gunes, Figen Varlioglu Yaylali, Zeynep Gözükara Karabağ, Xiaoxin Gao, Olga A. Syzgantseva, Aliekber Karabag, Gulsevim Bensu Yildirim, Konstantin Tsoi, Naoyuki Shibayama, Hiroyuki Kanda, Alwani Imanah Rafieh, Liping Zhong, Andreas Züttel, Paul J. Dyson, Selçuk Yerci, Mohammad Khaja Nazeeruddin, Görkem Günbaş
Abstract
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.