Kanagawa Accademy of Science and Technology
Organic Solar Cell Assessment Project

Research Target

Project Leader: Dr. Katsuhiko Takagi (KAST Technical Adviser)
Investigation period: 2011-

KAST participated in the FIRST program, entitled “Future Low Carbon Lifestyle with Organic Solar Cells”, that investigated dye-sensitive solar cells and organic photovoltaics by evaluating their performance. The project theme was “developing standards for analyzing and evaluating organic solar cell performance”. We aim to establish new internationally recognized analytical evaluation methods and standards for organic solar cell performance and develop elemental and innovative technologies for dye-sensitized (DSC) and thin-film organic solar cells.
FIRST: National Project lead by the Council for Science and Technology Policy (CSTP) in Cabinet Office, Government of Japan. (Funding Program for world-leading Innovative R&D on Sci. & Tech.)

Outline of FIRST Program

CSTP selected the 30 top researchers (called “core researchers”) that had the highest potentials from various fields and entrusted each core researcher with a research fund ranging between ¥1.5 and 6 billion over a period of 5 years.

Prof. Hiroshi Segawa (Tokyo Univ.) was selected one of the core researchers.

Organic solar cells are next-generation low-cost solar cells and their practical application is long-awaited. His proposal “Future Low Carbon Lifestyle with Organic Solar Cells” aiming at widespread applications of organic solar cells that will overturn conventional thinking and at acceleratinge R&D in this area through an all-Japanese team involving industry, government, and academia.

Research themes

For DSC

 Problems plaguing DSCs are low conversion efficiency and durability. Durability can be improved by using non-liquid electrolytes.
 Efficiency gains can be obtained by rational design of dye/semiconductor/electrolyte combinations.

For OPV

 Production cost of organic thin film solar cells is expected to be dramatically reduced by using ink organic semiconductors and printing techniques.

Common Aspects

 Direct application of existing IEC standards for Si cells to organic solar cells has serious drawbacks due to their different working principles.
 Spectral responsivity varies excessively with assembly process, components, and/or materials.

Our main equipment

Solar Simulator: Yamashita Denso YSS-T150A with thermostat chamber


The light source of this solar simulator consists of xenon and halogen lamps. The spectral mismatch is less than 3% according to IEC60904-9.

Attachment to solar simulator for calibration and for measurement at variable angles

Spectral response measurement device: Bunkoukeiki, CEP-2000MLQR


Irradiation frequency and intensity of pulsed monochromatic illumination were varied from 0.3 to 85 Hz and from 0.5 to 4.0 mW cm-2, respectively. The intensity of white bias irradiation was also varied from 0 to 1 sun.

Characterization examples

1) I-V measurements

 Difference between Si cells and DSCs are introduced.
 DSC efficiency varies little with increasing temperature, whereas Si cell efficiency decreases linearly with a maximum at about 40-60℃.
 Maximum points at about 10-20 mW/cm2 are also found on varying the light intensity.

2) Spectral Response

Dependence on monochromatic light intensity
 In the DC method, a nearly linear relationship between the short-circuit current density and the monochromatic light intensity is observed over a wide intensity range. The same results were also obtained by the AC method.