OLED Microprism Pitch Angle Optimization for Light Yield
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Solution Overview
Problem
Existing light-emitting arrangements, such as OLEDs and QLEDs, face limitations in external light yield due to total reflection and absorption of light at the edge layer surface, which conventional decoupling optics do not adequately address, especially given the varied optical properties of different OLED and QLED types.
Innovation Solution
The design of microprisms on the edge layer's surface, with specific pitch angles chosen to match the refractive index and wavelength-dependent light intensity maxima, allows for improved light emission by refracting light into the external space, increasing light yield through optimized optical elements that adapt to the specific emission spectrum and angular distribution of each type of OLED or QLED.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional decoupling optics (truncated pyramids or prisms) are used on the edge layer surface, then light extraction efficiency is partially improved, but the improvement is limited and insufficient for different OLED/QLED types with varied optical properties
Solution Approach 1:
The patent applies parameter changes by varying the pitch angle of microprism optical elements to match the specific optical parameters (refractive index, emission spectrum, angular distribution) of different OLED or QLED types. This allows the same microprism structure to be optimized for different light-emitting devices by adjusting geometric parameters rather than changing the entire optical element design.
Solution Approach 2:
The patent implements local quality by positioning microprism optical elements with specific pitch angles at locations corresponding to local maxima of light intensity in the emission spectrum. Different regions of the edge layer surface have microprisms with different pitch angles tailored to the local optical properties, maximizing light extraction at each spectral peak.
2Ease of manufacture
If the edge layer surface is left flat, then the structure is simple, but total reflection at the surface causes significant light absorption and reduces external light yield
Solution Approach 1:
The patent uses microprism optical elements with curved or angled surfaces instead of a flat edge layer surface. The microprisms have pitch angles greater than zero relative to the plane of the edge layer, creating non-planar surfaces that refract light at angles that prevent total internal reflection and reduce light absorption.
3Device complexity
If microprisms with fixed pitch angles are used, then the structure is simple to manufacture, but they cannot adapt to the wavelength-dependent angular distribution of light intensity in different OLED/QLED types
Solution Approach 1:
The patent changes the pitch angle parameter of microprisms based on the wavelength-dependent angular distribution of light intensity. By calculating the function I(λ,α) for each OLED or QLED type and identifying maxima, the pitch angles are optimized to match the specific emission characteristics, thereby maximizing external light yield for each device type.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly enhances the external light yield by aligning the microprism pitch angles with the absolute and local maxima of light intensity, ensuring that light is efficiently directed outward, thereby overcoming the limitations of conventional decoupling optics.
Implementation Method 1
optical elements, in particular in the form of microprisms, which have surface areas with a pitch angle β>0° relative to the plane E
Implementation Method 2
the light-generating layer 2 being arranged between the two electrodes 21, 22 and generating a light when a current is applied to the electrodes 21, 22
Implementation Method 3
there is a total reflection if the angle α larger than the corresponding critical angle αC is
Data Source
Figure 1~2b
Figure 3a~4b
Figure 5a~7
AI summary
The invention relates to a light-emitting arrangement with a light-generating layer of an OLED or QLED that generates light, which is emitted by a surface layer (4) into an exterior space (A). The surface layer (4) has a surface region running in a first approximation in a plane (E) through which the light is emitted. To achieve as great a light yield as possible, optical elements (3) are arranged or formed on this surface region of the surface layer (4), said optical elements having surface regions (5) with a pitch angle beta greater than 0° over plane (E). Pitch angle beta is selected such that it satisfies the equation n(lambda0) sin (beta - alpha0) = sin (beta), wherein the function I = I(lambda, alpha), alpha > 0°, which indicates the intensity I of the light within the surface layer (4) as a function of the wavelength lambda and the angle alpha, at which the light is diffused with reference to a normal (N) of the plane (E) extending from the light generating layer (2), is at its absolute maximum at wavelength lambda0 and at angle alpha0 and wherein n(lambda0) designates the refractive index of the optical elements (3) at wavelength lambda0.