Influence of Alkoxy Chain Length on the Properties of Two-Dimensionally Expanded Azulene-Core-Based Hole-Transporting Materials for Efficient Perovskite Solar Cells |
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Authors: | Dr Minh Anh Truong Dr Jaehyun Lee Tomoya Nakamura Dr Ji-Youn Seo Mina Jung Masashi Ozaki Ai Shimazaki Dr Nobutaka Shioya Prof Dr Takeshi Hasegawa Prof Dr Yasujiro Murata Dr Shaik Mohammed Zakeeruddin Prof Dr Michael Grätzel Dr Richard Murdey Prof Dr Atsushi Wakamiya |
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Institution: | 1. Institute for Chemical Research, Kyoto University, Uji, Kyoto, 611-0011 Japan;2. Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Station 6, CH-1015 Lausanne, Switzerland |
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Abstract: | A series of two-dimensionally expanded azulene-core-based π systems have been synthesized with different alkyl chain lengths in the alkoxy moieties connected to the partially oxygen-bridged triarylamine skeletons. The thermal, photophysical, and electronic properties of each compound were evaluated to determine the influence of the alkyl chain length on their effectiveness as hole-transporting materials (HTMs) in perovskite solar cells (PSCs). All the synthesized molecules showed promising material properties, including high solubility, the formation of flat and amorphous films, and optimal alignment of energy levels with perovskites. In particular, the derivatives with methyl and n-butyl in the side chains retained amorphous stability up to 233 and 159 °C, respectively. Such short alkoxy chains also resulted in improved electrical device properties. The PSC device fabricated with the HTM with n-butyl side chains showed the best performance with a power conversion efficiency of 18.9 %, which compares favorably with that of spiro-OMeTAD-based PSCs (spiro-OMeTAD=2,2′,7,7′-tetrakisN,N-bis(p-methoxyphenyl)amino]-9,9′-spirobifluorene). |
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Keywords: | amorphous materials conformation analysis energy conversion hole-transporting materials perovskite solar cells |
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