Dr. Takeshi FUKUDA, Assistant Professor, Saitama University, Faculty of Engineering, Department of Functional Materials Science, 255 Shimo-Okubo, Sakura-ku, Saitama 338-8570, Japan

Biography: Dr. Takeshi Fukuda received B.E. and M.E. from Waseda University, Tokyo, Japan, in 1999 and 2001, respectively. In 2001, he joined Fujikura Ltd. He received Ph.D. degree from Shinshu University, Nagano, Japan, 2008. Since 2008, he has been the assistant professor with the department of functional materials science, Saitama University, Saitama, Japan. His research interests are organic-inorganic thin film devices (photovoltaic cells, light-emitting diodes, thermoelectric devices, and wavelength selective organic photoconductive devices), electrospray deposition method, and semiconductor quantum dots and related sensing materials. In addition, he interested in several characterization techniques such as Raman spectroscopy, displacement current measurements, and optical measurement.

Speech Title: Raman spectroscopy and GIWAXD analysis of electrospyraed organic photovoltaic material
Abstract: An electrospray deposition has been investigated as a novel coating process, and the molecular orientation can be controlled by optimizing the evaporation speed of organic solvent. Nowadays, our research group already demonstrated the highly oriented polymer and the high photoconversion efficiency can be realized by the electrospray deposition process. In this research, we investigated the Raman spectroscopy and GIWAXD analysis for poly(3-hexylthiophene-2,5-diyl)] (P3HT) and poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]] (PTB7), which are used as p-type polymer in an organic photovoltaic cell.
In the case of P3HT, the edge-on oriented P3HT increased with increasing solvent evaporation time in the electrospray deposition, which was evaluated using an optical microscope placed bellow the substrate. As a result, the photoconversion efficiency was linearly increased with increasing solvent evaporation time even though the device was not annealed after depositing the P3HT: PCBM layer.
On the other hand, the PTB7 in the blended film with PCBM was successfully aligned by optimizing the solvent evaporation time as same as the P3TH case. Therefore, the optimized solvent evaporation time is an important factor for realizing high photovoltaic performance of the electrospray deposition method.
Keywords: Organic photovoltaic cell; Electrospray deposition; Raman spectroscopy; GIWAXD Analysis