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Flexible energy sources and storage devices

In this day and age, which some have referred to as the “Ubiquitous Era,” renewable energy resources and flexible storage devices are essential to ensure the progress of printing technology which is growing in importance. Furthermore, in order to realize the technological benefits of such an era, printing technology will be at the core of research into the efficiency of flexible mobile devices, wearable computers, electronic papers, to mention only a few, which will only increase in popularity.

1) Polymer solar cells

Based on sensible solution-based processes, low cost and flexible polymer solar cells will be fabricated through various printing technologies. These printable polymer solar cells possess several merits in relation to inorganic solar cells, which are currently in use, for the following reasons

  • Processible solutions and easy fabrication
  • Controllable layer-by-layer structures
  • Flexible thin film devices

Towards the goal of improving polymer solar cells, technical know-how and high-tech printing process are essential prerequisites for low-cost and renewable energy resources. With that in mind, Prof. Kwanghee Lee (GIST) has been developing highly efficient polymer solar cells by closely collaborating with the Center for Polymers and Organic Solids (CPOS) in UCSB (Prof. A. J. Heeger). Through collaboration with the CPOS group in UCSB, GIST achieved a world record of 6.5 % in PCE efficiency by utilizing all-solution processing to fabricate these all important polymer solar cells. Furthermore, they expect to see the fruition of processible flexible devices with polymer ink by collaborating further with Konarka Technology (technical adviser: A. J. Heeger), which is the pioneer company in printing electronics.

Flexible radical battery

2) Flexible energy storage devices

Together with flexible polymer solar cells, flexible batteries are critical for the spread of ergonomic devices in this “ubiquitous world.” In order to see the fruition of this flexible battery, we also need flexible electrodes, such as radical polymer electrodes, for the following reasons

  • Faster charging and discharging than inorganic electrodes
  • Large capacitance
  • Flexible and light devices

In general, the process involved in electric charging and discharging of secondary batteries are closely linked with the movements of electrons and counter-ions on the surfaces of electrodes. In flexible lithium-ion batteries, inorganic electrodes have been used and continue to be used to date. It’s been determined that electrons and counter-ions act slower in inorganic nano structures. Recently, Prof. H. Nishide (Waseda Univ.) has developed the conceptual use of radical polymer batteries to address this challenge. When flexible polymer electrodes are introduced into radical batteries, vast amounts of electricity can be charged and discharged very rapidly. In addition, polymer electrodes can be printed through solution-based printing technology which further complements the entire process.

3) Synthesis of new polymers

In the development of renewable energy devices, the synthesis of new materials is one of the most important issues with which to meet the following goals

  • High efficient conjugated polymers for solar cells
  • New materials for electro-optical devices
  • Functional materials for the printing technology

The creation of more efficient materials is one of the most earnest wishes for those who research organic electronics, especially in the realm of polymer solar cells. Consequently, Prof. Jae-suk Lee (GIST) has synthesized efficient and environment-friendly polymers for use in organic electronics. The new polymers are expected to be utilized not only for use in high efficient polymer solar cells, but also with other kinds of electro-optical devices through the development of printing technology.

Portable energy devices in the ubiquitous world