OLED outcoupling films
Written by Microsharp
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A large proportion of the light produced by OLED’s is trapped as ‘waveguided modes’ inside the OLED due to the effects of total internal reflection, particularly at the substrate/air interface.  In effect, a lot of the light rays emitted at angles away from the vertical cannot come out of the OLED as they ‘see’ the interface with air as a mirrored surface. A surface structured out-coupling film enables these waveguided modes to be emitted by changing the incident angle as shown in the figures below. The result is a gain of 30% - 70% in the total light emitted by the OLED.

 

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 Microsharp and OLED Out-Coupling

Microsharp is at the forefront of OLED out-coupling development due to our participation in www.OLED100.eu,  a major pan European project to develop high efficiency large area OLED’s for use in lighting applications. The project involves many of the major players in European OLED developments.

Within the project, Microsharp developed and manufactured a number of microstructures to optimise out-coupling from glass to air in a range of OLED devices.

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Microsharp Out-Coupling Structures

Each OLED device has its own unique emission profile. To maximise the out-coupling efficiency it is important to use an out-coupling structure designed to work with the precise characteristics of the OLED. Microsharp has extensive expertise in the design, modelling and testing of new and novel structures gained working in conjunction with leading OLED developers. Independent testing of structures designed and manufactured by Microsharp has confirmed that our structures out-performed those of structures available from other sources.   

Integrating Out-Coupling and Light Management

The integration of a microstructured optical film on the surface of the OLED enables more options than simply improving the efficiency of the device. By modifying the surface microstructures the direction and intensity of the light emitted by the OLED can be manipulated to create a variety of effects.

The out-coupling optical features can be modified to provide additional light redirection (at a slight loss to the out-coupling efficiency), so that the same film can for example make the OLED comply with anti-glare standards for office fittings, provide an asymmetric ‘wall washer’ light pattern, or give a ‘bat wing’ two beam strip emission useful in retail. In this way a single OLED design, coupled with different surface films, produces a range of lighting products.

Microsharp Products and Services

Microsharp has extensive expertise and experience in the development of bespoke out-coupling structures optimised to work with specific OLED devices. We can design, develop and manufacture structures that will provide the optimum light out-coupling efficiency. We can also design structures that can manipulate the exit beam angle to produce a specific light output characteristic.

Microsharp can produce seamless unitary structured film areas up to 1 m by 0.5 m in size. Structures can then be manufactured on our in-house, state of the art U.V casting facility.  Large area films are produced on a continuous reel to reel process up to 100 cm wide. The inherent flexibility of our existing production unit allows for efficient production of both test quantities and commercial scale production of up to 1 million m2 per year.

 Existing Products.

We have designed and manufactured a number of out-coupling structures that can be made available to customers as evaluation samples.

The following stucture is one example HSS MLA 70 / 24.5 250 PMMA 

To order samples click here  

 

 

 Production Capability

Individual, seamless, unitary structures up to 1000 mm by 600 mm in area are possible. Our in-house manufacturing facilities can produce over 1 million m2 of film annually.

Acknowledgement

The work leading to the development of these films has received funding from the European Community's Seventh Framework Program under grant agreement FP7–224122