Bright Future for Next-Generation Organic Lighting Systems; High-performance Polymer-Based White-Light-Emitting Electrochemical Cells

Significance 

Recent technological advancement has seen significant improvements in the fields of display and lighting. This has attracted significant attention of many researchers owing to the ever-increasing demand of such devices like smartphones. To this note, researchers have been looking for alternatives and have identified organic light emitting diodes as a promising solution for meeting the new applications demand. They exhibit excellent properties like flexibility and lightweight.

Among the available types of organic light emitting diodes, light-emitting electrochemical cells have remarkable advantages over the organic light emitting diodes. They can be produced in large scale at low costs and also use air stable electrode. On the other hand, polymer-based light-emitting electrochemical cells are compatible with roll-to-roll coating and solution-based screen printing. Generally, lighting and display applications require white light. White light-emitting electrochemical cells can be achieved through light mixing methods that comprises of red-green-blue. To improve their efficiency, they have been fabricated using iridium phosphorous as the guest and fluorescent conjugated polymer as the host.

Recently, a group of researchers at Waseda University: Tetsuyuki Cho, Professor Kenichi Oyaizu and Professor Hiroyuki Nishide and led by Professor Yoshinori Nishikitani in collaboration with Dr. Soichi Uchida and Dr. Suzushi Nishimura at JXTG Nippon Oil & Energy Corporation developed a white polymer-based light-emitting electrochemical cells with significantly high color rendering indices. Their research work is published in the research journal, ChemPlusChem.

Briefly, the authors commenced their experimental work by fabricating the light-emitting electrochemical cells using blended films of emitting materials consisting of red-phosphorescent iridium complexes and blue-green fluorescent polyfluorenes. They purposed to obtain very high color rendering indices and suitable Commission de Internationale de I’Eclairage coordinates through red-blue-green color mixing.

From the experimental results, the authors observed efficient energy transfer from the excited poly(9,9-dioctylfluorene-co-benzothiadiazole) to iridium complexes. This was attributed to the emission mechanism property of the light-emitting electrochemical cells. Consequently, for white light-emitting electrochemical cells, the emission color was tuned by changing the mixing ratio of materials. This was a superior advantage of utilizing mixed films of red-phosphorescent iridium complexes and blue-green fluorescent polymers as compared to single emitter systems. Furthermore, high color-rendering indices were achieved effectively using blue-green-red light mixing strategy than by using only two-color systems.

In a nutshell, the research team successfully developed white light-emitting electrochemical cells with distinct properties and efficiency as compared to the initially made organic light emitting diodes. For instance, they exhibit very high color-rendering indices which makes them a promising solution for numerous applications in lighting and displays and beyond. Therefore, light-emitting electrochemical cells based on blue-green fluorescent conjugated polymer and red iridium complexes are not only a promising solution to the design and construction of high-performance white light emitting devices but also a platform for future studies aimed at improving the functionality of such devices.

About the author

Name: Yoshinori NISHIKITANI
Title: Professor, Docteur (l’Université Paris-Nord)
Affiliation: Research Institute for Science and Engineering, Waseda University, Ohkubo 3-4-1, Shinjuku-ku, Tokyo 169-8555, Japan.
TEL: +81-3-5286-3370, FAX: +81-3-3209-5522, Email: [email protected]

Education:
1978-1980  Kyoto University, Graduate School, Hydrocarbon Chemistry, MSc
1974-1978  Kyoto University, Undergraduate course, Hydrocarbon Chemistry, B.S.

Professional Experience:
2018-Pres.  Professor, Research Institute for Science and Engineering, Waseda University.
2013-2018  Professor, Department of Advanced Science and Engineering, Waseda University.
2011-2013  Executive Researcher, Central Technical Research Laboratory, JX Nippon Oil & Energy Corporation.
2004-2011  Deputy General Manager, Central Technical Research Laboratory, Nippon Oil Corporation.
1998-2004  Group Manager, Central Technical Research Laboratory, Nippon Oil Corporation.
1994-1998  Senior Researcher, Central Technical Research Laboratory, Nippon Oil Corporation.
1989-1994  Research Chemist, Central Technical Research Laboratory, Nippon Oil Corporation.
1987-1989  Visiting Scientist, Le Centre National de la Recherche Scientifique (CNRS), Thiais, France, F. Garnier Laboratory.
1980-1987  Research Chemist, Central Technical Research Laboratory, Nippon Oil Corporation.
2004-2004  Lecturer (part-time), The University of Tokyo.
2005-2006  Lecturer (part-time), Nagoya Institute of Technology.
2012-Pres.  Visiting Professor, Molecular Engineering Institute, Kinki University.
2013-Pres.  Visiting Professor, Multi-Energy Innovation Center, Nagoya Institute of Technology

Research Interests: Quantum Chemistry, Electrochemistry, Photoelectrochemistry, Solar Energy Conversion, Hydrogen Generation & Storage, Organic Device (Battery, Solar Cell, Light-Emitting Device)

Funding Information:
1999-2004 Leader of PEC (Petroleum Energy Center) Grant; Priority Area, “Effective Use of Petroleum”

Committee Services:
2006-2008  Director, The Japanese Photochemistry Association
2008-2010  Director, The Chemical Society of Japan,
2009-2016  Research Advisor, JST CREST Program “Creative Research for Clean Energy Generation Using Solar Energy”
2009-2016  Research Advisor, JST PREST Program “Photoenergy Conversion Systems and Materials for the Next Generation Solar Cells”
2010-Pres.  Research Advisor, JST ALCA Program “Solar Cell and Solar Energy Systems”
2017-Pres.  Research Advisor, JST MIRAI Program

Scientific Publications and Patents:
Article (Peer-Reviewed): 37
Book (subdivision): 17
Patent: over 110

Reference

Nishikitani, Y., Cho, T., Uchida, S., Nishimura, S., Oyaizu, K., & Nishide, H. (2018). Polymer-Based White-Light-Emitting Electrochemical Cells with Very High Color-Rendering Index Based on Blue-Green Fluorescent Polyfluorenes and Red-Phosphorescent Iridium Complexes. Chempluschem, 83(5), 463-469.

Go To Chempluschem

Check Also

Advancing Discovery and Growth of Crystalline Materials using Continuous-Flow, Well-Mixed Microfluidic Devices - Advances in Engineering

Advancing Discovery and Growth of Crystalline Materials using Continuous-Flow, Well-Mixed Microfluidic Devices