Hole-Transporting Materials Using Quasiplanar Skeletons for Efficient Perovskite Solar Cells: Effects of Lengths of Alkoxy Chains
Yasujiro Murata a, Atsushi Wakamiya a, Ai Shimazaki a, Masashi Ozaki a, Mina Jung a, Jaehyun Lee a, Hidetaka Nishimura a
a Kyoto University, Goryo-Ohara, Nishikyo-ku, Kyoto 615-8245, Japan
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of International Conference Asia-Pacific Hybrid and Organic Photovoltaics (AP-HOPV17)
Yokohama-shi, Japan, 2017 February 2nd - 4th
Organizers: Tsutomu Miyasaka and Iván Mora-Seró
Poster, Jaehyun Lee, 029
Publication date: 7th November 2016

 Perovskite solar cells (PSCs) have attracted much attention as cost-effective next generation photovoltaics. In order to further improve the device performance, it should be crucial to develop an excellent hole-transporting material (HTM) that can effectively collect holes generated in perovskite layer. We have reported a novel HTM, HND-Azulene, using four oxygen-bridged triarylamines around an azulene core.1 This HTM having n-octyl groups was found to be superior in comparison with the currently used standard material, Spiro-OMeTAD, in PSCs. For further improvement of the device performance, we newly synthesized the derivatives of this system with a variety of alkoxy groups.

 The hole mobilities of these derivatives were measured by the space-charge-limitation of current (SCLC) method. Our PSCs are composed of the following structure: FTO / compact-TiO2 / mesoporous-TiO2 / perovskite CH3NH3PbI3 / HTM / Au. The perovskite layers were prepared according to one-step solution method with solvent engineering.

 The SCLC measurements on these HND-Azulene derivatives revealed that their hole mobility increases as the length of alkoxy chains shortened (-OR = octyloxy < hexyloxy < butoxy < methoxy). In order to investigate the effects of alkoxy chain length on the performance in PCSs, the devices using methoxy-azulene and octyl-azulene as HTMs were fabricated. The methoxy-azulene (17.0%) showed higher PCE value in comparison with octyl-azulene (15.1%).

 In this presentation, the effects of the chain length of alkoxy groups on the performance of PSCs as well as on the solid state properties will be discussed in detail.

[1] H. Nishimura, N. Ishida, A. Shimazaki, A. Wakamiya, A. Saeki, L. T. Scott, and Y. Murata, J. Am. Chem. Soc. 2015, 137, 15656.

 



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