Author(s)

Yosei Shibata, Takahiro Kono, Takahiko Suzuki, Yuzuru Narita, Fumihiko Hirose, Yuji Yoshida

Graduate School of Science and Engineering, Yamagata University, Yonezawa, Japan.
Research Center for Photovoltaic Technologies, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan.

Recently, power conversion efficiencies of organic photovoltaics based on small molecules have been dramatically improved by means of the bulk heterojunction (BHJ) structure. Moreover, to optimize photovoltaic performance, thermal annealing treatments have often been used because of the simplicity of the process. However, the elucidation of effects of thermal annealing treatment on BHJ film structure based on small molecules is still not enough. Here, we report the results of structural analysis with synchrotron radiation of α-sexithiophene:fullerene BHJ films before and after thermal annealing treatment. In particular, the open-circuit voltage was increased to as high as 0.72 V; moreover, the BHJ films based on α-sexithiophene and fullerene were also clearly crystallized by the thermal annealing treatment. In this study, we found that the optimal crystal size existed in BHJ films for high-performance organic photovoltaics.

Organic Photovoltaics, Oligothiophene, Bulk Heterojunction Structure, Thermal Anneal, Morphological Control

Shibata, Y. , Kono, T. , Suzuki, T. , Narita, Y. , Hirose, F. and Yoshida, Y. (2014) Structural Analysis of Thermally-Annealed Bulk Heterojunction Films Based on Sexithiophene and Fullerene. Advances in Materials Physics and Chemistry, 4, 127-133. doi: 10.4236/ampc.2014.47015.