OLED out-coupling films
Written by Microsharp
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A large proportion of the light produced by OLED’s is trapped 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 improved light out-coupling of up to 38% .



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 perform as well as the best in class 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 38%. 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.

Evaluation Sample

Samples of the Hexagonally packed HemiSpherical (HHS), Micro Lens Array (MLA) structure produced on the surface of a 250 μm thick PMMA base film. can be ordered via this website link to sample ordering web page

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