Tetrapodal Hole‐Collecting Monolayer Materials Based on Saddle‐Like Cyclooctatetraene Core for Inverted Perovskite Solar Cells

• Published in: Angewandte Chemie Vol. 136; no. 46
• Main Authors: Truong, Minh Anh, Ueberricke, Lucas, Funasaki, Tsukasa, Adachi, Yuta, Hira, Shota, Hu, Shuaifeng, Yamada, Takumi, Sekiguchi, Naomu, Nakamura, Tomoya, Murdey, Richard, Iikubo, Satoshi, Kanemitsu, Yoshihiko, Wakamiya, Atsushi
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 11.11.2024
• Subjects: chemisorption; cyclooctatetraene; Energy conversion efficiency; hole-collecting material; monolayer; Monolayers; perovskite solar cell; Perovskites; Phosphonic acids; Photovoltaic cells; Solar cells; Structural stability; Substrates; Wettability
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.202412939

Hole‐collecting monolayers have greatly advanced the development of positive‐intrinsic‐negative perovskite solar cells (p‐i‐n PSCs). To date, however, most of the anchoring groups in the reported monolayer materials are designed to bind to the transparent conductive oxide (TCO) surface, resulting in less availability for other functions such as tuning the wettability of the monolayer surface. In this work, we developed two anchorable molecules, 4PATTI‐C3 and 4PATTI‐C4, by employing a saddle‐like indole‐fused cyclooctatetraene as a π‐core with four phosphonic acid anchoring groups linked through propyl or butyl chains. Both molecules form monolayers on TCO substrates. Thanks to the saddle shape of a cyclooctatetraene skeleton, two of the four phosphonic acid anchoring groups were found to point upward, resulting in hydrophilic surfaces. Compared to the devices using 4PATTI‐C4 as the hole‐collecting monolayer, 4PATTI‐C3‐based devices exhibit a faster hole‐collection process, leading to higher power conversion efficiencies of up to 21.7 % and 21.4 % for a mini‐cell (0.1 cm2) and a mini‐module (1.62 cm2), respectively, together with good operational stability. This work represents how structural modification of multipodal molecules could substantially modulate the functions of the hole‐collecting monolayers after being adsorbed onto TCO substrates. A series of tetrapodal hole‐collecting monolayer materials based on a saddle‐like cyclooctatetraene core were developed. These molecules were found to form monolayers on transparent electrode substrates, with some phosphonic acid anchoring groups pointing upward, resulting in hydrophilic surfaces. The perovskite solar cell devices using these hole‐collecting monolayers exhibit high power conversion efficiencies of up to 21.7 % and good operational stability.