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Proceedings Paper

Organic photovoltaic cell based on benzoporphyrin with p-i-n junction
Author(s): Yoshiharu Sato; Takaaki Niinomi; Yoko Abe; Yutaka Matsuo; Eiichi Nakamura
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Paper Abstract

We have fabricated organic photovoltaic cell using tetrabenzoporhyrin (BP) as a donor material. Tetrabenzoporhyrin is formed by thermal conversion of the soluble precursor that has four bicyclo rings. Upon heat treatment above 150°C, the precursor molecule is converted to semiconductive tetrabenzoporphyrin, which is insoluble against conventional organic solvents. Taking advantage of this insoluble character of BP, p-i-n bulk heterojunction photovoltaic cell is successfully fabricated from solution, with BP/BP:fullerene/fullerene trilayer, where p-layer is crystal BP, i-layer consists of both BP and fullerene, and fullerene acts as n-layer. We have reported the p-i-n photovoltaic cell using [6,6]-phenyl-C61-butyric acid n-butyl ester (PCBNB) as an acceptor. This solution-processed p-i-n device has achieved power conversion efficiency as high as 3.4% (Jsc=9.8mA/cm2; Voc=0.62V; FF=0.56). The performance of BP device with p-i-n junction is further improved by introducing a new fullerene for the i- and n-layers. Taking into consideration LUMO level, solubility and thermal properties, a novel fullerene derivative, 1,4-bis(dimethylphenylsilylmethyl)[60]fullerene (SIMEF), is designed and synthesized. This new di-adduct fullerene , SIMEF, improves power conversion efficiency up to 4.1% (Jsc=9.1mA/cm2; Voc=0.76V; FF=0.59). This improvement is largely due to an increased Voc. We have analyzed BP:fullerene composite films to find that formation of meta-stable phase of BP is fully suppressed by SIMEF. Depth profile of this p-i-n cell is measured by means of TOF-SIMS method to observe the expected vertical distribution of the donor and acceptor that has been designed.

Paper Details

Date Published: 26 August 2008
PDF: 9 pages
Proc. SPIE 7052, Organic Photovoltaics IX, 70520J (26 August 2008); doi: 10.1117/12.795638
Show Author Affiliations
Yoshiharu Sato, Japan Science and Technology Agency (Japan)
Takaaki Niinomi, Japan Science and Technology Agency (Japan)
Yoko Abe, Japan Science and Technology Agency (Japan)
Yutaka Matsuo, Japan Science and Technology Agency (Japan)
Eiichi Nakamura, Japan Science and Technology Agency (Japan)
The Univ. of Tokyo (Japan)

Published in SPIE Proceedings Vol. 7052:
Organic Photovoltaics IX
Zakya H. Kafafi; Paul A. Lane, Editor(s)

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