4 OPV with a Crystalline Organic Pigment Active Layer Up to 10 μm
8 5
to 10 μm. The material used in this study was a combination of the well-known
organic pigment fullerene (C 60 ), a soccer-ball-shaped molecule, and phthalocyanine, which is also well known as a paint material, and these have been a standard
donor:acceptor combination for vacuum-deposited OPVs for decades. Usually, the
efficiency of organic solar cells using this combination of organic pigments decreases
when the thickness exceeds 40–50 nm, but by growing the organic pigment crystals
in an appropriate size (diameter of about 100 nm) (Fig. 4.3), the efficiency hardly
decreased even when the thickness was increased to 10 μm (Fig. 4.1b). In addition, we demonstrated the relationship between the light absorbed by the organic
pigment and the generated current in a wide range of thicknesses (40 nm–1 μm) in
a corresponding manner (Fig. 4.4).
The thickness of 10 μm itself achieved in this study is much larger than the
thickness that absorbs almost all visible light, so it cannot be directly applied to
the OPV or organic light-emitting diode products. However, the potential of organic
pigments, which are usually used in a thickness of several nm to several tens of nm,
has been proved to work as a photoelectric conversion layer even with a thickness
of 10 μm, which is an order of magnitude thicker than previously thought. We hope
this fact will promote R&D of future organic photoelectric conversion devices using
crystalline organic pigments.
Acknowledgments This section is written based on the results of collaboration with Mr. Mikimasa
Katayama (at that time) at Tokyo University of Agriculture and Technology, and Professor Masahiro
Hiramoto and Dr. Satoshi Nakao (at that time) at the Institute for Molecular Science. We would like
to thank Professor C.W. Tang and Assistant Professor S. Dong at Hong Kong University of Science
and Technology for their discussion and advices. In addition, part of the research introduced in this
section was carried out with the support of JST-ALCA, JSPS Scientific Research Fund (17H04807),
and Nanotechnology Platform Project (Molecular/Material Synthesis).
References
1. Meng, L. et al. Organic and solution-processed tandem solar cells with 17.3% efficiency.
Science 361, 1094–1098 (2018)
2. Kang, H., et al.: Bulk-heterojunction organic solar cells: five core technologies for their
commercialization. Adv. Mater. 28, 7821–7861 (2016)
3. Søndergaard, R., Hösel, M., Angmo, D., Larsen-Olsen, T.T., Krebs, F.C.: Roll-to-roll
fabrication of polymer solar cells. Mater. Today 15, 1–2 (2012)
4. Dou, L., et al.: 25th anniversary article: a decade of organic/polymeric photovoltaic research.
Adv. Mater. 25, 6642–6671 (2013)
5. Roncali, J., Leriche, P., Blanchard, P.: Molecular materials for organic photovoltaics: small is
beautiful. Adv. Mater. 26, 3821–3838 (2014)
6. Mishra, A., Bäuerle, P.: Small molecule organic semiconductors on the move: promises for
future solar energy technology. Angew. Chem. Int. Ed. 51, 2020–2067 (2012)
7. Kaji, T., et al.: Co-evaporant induced crystalline donor: acceptor blends in organic solar cells.
Adv. Mater. 23, 3320–3325 (2011)
8. Song, B., Rolin, C., Zimmerman, J.D., Forrest, S.R.: Effect of mixed layer crystallinity on the
performance of mixed heterojunction organic photovoltaic cells. Adv. Mater. 26, 2914–2918
(2014)
8 5
to 10 μm. The material used in this study was a combination of the well-known
organic pigment fullerene (C 60 ), a soccer-ball-shaped molecule, and phthalocyanine, which is also well known as a paint material, and these have been a standard
donor:acceptor combination for vacuum-deposited OPVs for decades. Usually, the
efficiency of organic solar cells using this combination of organic pigments decreases
when the thickness exceeds 40–50 nm, but by growing the organic pigment crystals
in an appropriate size (diameter of about 100 nm) (Fig. 4.3), the efficiency hardly
decreased even when the thickness was increased to 10 μm (Fig. 4.1b). In addition, we demonstrated the relationship between the light absorbed by the organic
pigment and the generated current in a wide range of thicknesses (40 nm–1 μm) in
a corresponding manner (Fig. 4.4).
The thickness of 10 μm itself achieved in this study is much larger than the
thickness that absorbs almost all visible light, so it cannot be directly applied to
the OPV or organic light-emitting diode products. However, the potential of organic
pigments, which are usually used in a thickness of several nm to several tens of nm,
has been proved to work as a photoelectric conversion layer even with a thickness
of 10 μm, which is an order of magnitude thicker than previously thought. We hope
this fact will promote R&D of future organic photoelectric conversion devices using
crystalline organic pigments.
Acknowledgments This section is written based on the results of collaboration with Mr. Mikimasa
Katayama (at that time) at Tokyo University of Agriculture and Technology, and Professor Masahiro
Hiramoto and Dr. Satoshi Nakao (at that time) at the Institute for Molecular Science. We would like
to thank Professor C.W. Tang and Assistant Professor S. Dong at Hong Kong University of Science
and Technology for their discussion and advices. In addition, part of the research introduced in this
section was carried out with the support of JST-ALCA, JSPS Scientific Research Fund (17H04807),
and Nanotechnology Platform Project (Molecular/Material Synthesis).
References
1. Meng, L. et al. Organic and solution-processed tandem solar cells with 17.3% efficiency.
Science 361, 1094–1098 (2018)
2. Kang, H., et al.: Bulk-heterojunction organic solar cells: five core technologies for their
commercialization. Adv. Mater. 28, 7821–7861 (2016)
3. Søndergaard, R., Hösel, M., Angmo, D., Larsen-Olsen, T.T., Krebs, F.C.: Roll-to-roll
fabrication of polymer solar cells. Mater. Today 15, 1–2 (2012)
4. Dou, L., et al.: 25th anniversary article: a decade of organic/polymeric photovoltaic research.
Adv. Mater. 25, 6642–6671 (2013)
5. Roncali, J., Leriche, P., Blanchard, P.: Molecular materials for organic photovoltaics: small is
beautiful. Adv. Mater. 26, 3821–3838 (2014)
6. Mishra, A., Bäuerle, P.: Small molecule organic semiconductors on the move: promises for
future solar energy technology. Angew. Chem. Int. Ed. 51, 2020–2067 (2012)
7. Kaji, T., et al.: Co-evaporant induced crystalline donor: acceptor blends in organic solar cells.
Adv. Mater. 23, 3320–3325 (2011)
8. Song, B., Rolin, C., Zimmerman, J.D., Forrest, S.R.: Effect of mixed layer crystallinity on the
performance of mixed heterojunction organic photovoltaic cells. Adv. Mater. 26, 2914–2918
(2014)