[11a-S221-1~12] 12.5 Organic solar cells

▲ [11a-S221-11] Low-Temperature-Processed Brookite-Based TiO₂ Heterophase Junction Electron Transport Layer Boosts Performance of Planar Perovskite Solar Cells

〇Md Shahiduzzaman^1,2, Sem Visal², Mizuki Kuniyoshi², Tetsuya Kaneko², Shinjiro Umezu³, Tetsuhiro Katsumata², Satoru Iwamori², Masato Kakihana⁴, Tetsuya Taima¹, Masao Isomura², Koji Tomita² (1.Kanazawa Univ., 2.Tokai Univ., 3.Waseda Univ., 4.Tohoku Univ.)

Keywords:Brookite TiO2 nanoparticles., TiO2 heterophase junction, planar perovskite solar cells

Herein, we demonstrate the effects of different titanium oxide (TiO2) polymorphs, anatase and brookite as electron transport layers (ETLs) to enhance the efficiency of planar perovskite solar cells (PSCs). We design and fabricate low-temperature (<180 °C)-processed brookite based TiO2 heterophase junctions on fluorine-doped tin oxide (FTO) as the substrate. We investigate and compare anatase (A) and brookite (B) and heterophase anatase–brookite (AB) and brookite–anatase (BA) as ETLs in PSCs. The power conversion efficiencies (PCEs) of PSCs with low-temperature-processed FTO-B as the ETL were as high as 14.92% that is the highest reported efficiency of FTO-B-based single-layer PSC. This signifies that FTO-B acts as an active phase and can be a potential candidate as an n-type ETL scaffold in planar PSCs. Moreover, PSCs with heterophase junction FTO-AB ETLs showed PCEs as high as 16.82% that is superior to those of PSCs with anatase (FTO-A; 13.86%) and brookite (FTO-B; 14.92%) as the ETLs. Furthermore, the PSCs with FTO-AB revealed enhanced efficiency and minimized hysteresis compared with those with FTO-BA (13.45%) owing to the better-match band alignment with the perovskite layer, which resulted in superior photogenerated charge carrier extraction and reduced charge accumulation at the interface between the heterophase junction and perovskite, as evidenced by photoluminescence and electrochemical impedance spectroscopy. Therefore, the present work offers an effective strategy to develop heterophase junction ETLs and manipulate the interfacial energy band to further enhance the performance of planar PSCs and allow clean, and eco-friendly fabrication of low-cost mass production.
1. Shahiduzzaman, M.; Visal, S.; Kuniyoshi, M.; Kaneko, T.; Umezu, S.; Katsumata, T.; Iwamori, S.; Kakihana, M.; Taima, T.; Isomura, M.; Tomita, K. Nano Lett. 2018. (DOI: 10.1021/acs.nanolett.8b04744)