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Flexible Organic Opto-Electronics
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Flexible Opto-Electronics

 

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     Recently, the demand for flexible electronics increased a lot for the next generation electronics application. Especially, research about flexible displays and solid-state lighting devices based on organic light emitting diodes (OLED) has been stimulated. Moreover, flexible energy conversion devices such as organic/polymer photovoltaic cells (OPVs) are also important area in flexible electronics.

     With this movement in flexible device technology, many demonstrations has been made by several companies and research groups. However, new flexible electrode materials instead of using conventional brittle transparent oxide conductors are essentially needed for highly efficient flexible electronic device applications. Therefore, our group has been developing flexible soft anode material replacing conventional indium tin oxide (ITO) electrode.



Research Field

 

Flexible OLEDs:Flexible Anode

 

     We developed self-organized conducting polymer anode material which has tunable work-function (we call AnoHIL) for application to flexible OLED display. The work function value of the flexible AnoHIL has the range of 4.7~5.8eV which is actually the highest value among flexible anodes for current organic devices. In right scheme, AnoHIL has a role of transparent anode.


     Moreover, AnoHILs do not need additional hole injection layer (HIL) and it means simplifying of device structure as shown in the following figure


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AnoHILs have important three advantages better than ITO electrodes.

1) Transmittance over 95% in all the visible range

2) Ohmic contact between organics and the AnoHIL layer

3) Improvement of luminous efficiency and device lifetime.

   

  

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Solid State lighting

    Solid-state lighting (SSL) refers to a type of lighting that uses semiconductor light-emitting diodes (LEDs), organic light-emitting diodes (OLED), or polymer light-emitting diodes (PLED) as sources of illumination rather than electrical filaments, plasma (used in arc lamps such as fluorescent lamps), or gas. When compared to the incandescent or fluorescent lamp, OLED does not contain environmental hazardous materials, e.g., Hg, and also it can save up to 70% of power consumption of fluorescent lamp, 90% of that of incandescent lamp. Hence, in the near future, the incandescent lamp and the fluorescent lamp through the world will be replaced with environment-friendly solid-state white lighting source based light-emitting diodes. 
     Among the Solid State Lightings, OLED is the best candidate for the lighting application. When compared to the inorganic LED, it has various advantages since it can realize the 3 dimensional lighting, very thin device thickness, soft light similar to the sun and flexible lighting, etc.

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Research Field


     The development of OLED lighting source is getting more and more important. Until now, researchers in this field have tried to improve the luminous efficiency and the device lifetime, which have been the most important issues, by making tandem OLED structures. However, when we produce the OLED lighting panels based on tandem structures, we have to spend the more material cost and longer processing time. Therefore, to solve this importance issue, we tried to simplify the tandem white OLED devices.



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fe research    We are also endeavoring to achieve highly efficient flexible energy device using organic/polymer photovoltaic (OPV) device.

     The OPVs using our flexible AnoHIL anodes showed high power conversion efficiency which is comparable to the conventional ITO/PEDOT:PSS based OPV. As the work-function of anode increases, holes can be extracted efficiently from the photoactive layer in the OPV devices.

     We hope to attain further highly improved flexible photovoltaic devices in the near future.