Microcavity LED with Unpatterned White Layer

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Solution Overview

Problem

Existing LED devices face inefficiencies in light output and angular color performance due to trapped light and manufacturing complexities, particularly with patterned organic material deposition and color filters that absorb light and increase costs.

Innovation Solution

A light-emitting microcavity diode device with a reflective and semi-transparent electrode structure over a substrate, featuring an unpatterned white-light-emitting layer and patterned optical spacing elements to form microcavities that emit primary and complementary colors, reducing angular color change and increasing light output through constructive interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If optical cavity structures are used to increase light output, then light emission is improved, but angular color dependence becomes unacceptable

Engineering Contradiction:

Improvelight outputVSAvoidangular color dependence

Core Design Contradiction:

Illumination intensityVSStability of the object's composition

Solution Approach 1:

The device divides each pixel into multiple sub-pixels (red, green, blue) with different optical cavity thicknesses. Each sub-pixel has a tailored cavity that compensates for angular color shift at its specific wavelength, collectively achieving reduced angular color dependence across the full spectrum while maintaining high light output.

Inventive Principle:

Principle #1Segmentation

2Manufacturing precision

If patterned organic material deposition is used to form optical cavities, then color control is improved, but manufacturing complexity and difficulty to scale increase

Engineering Contradiction:

Improvecolor controlVSAvoidmanufacturing complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

Instead of patterning the organic light-emitting materials to form optical cavities (complex approach), the invention inverts the approach by using uniform organic layers and patterning the underlying electrode structures or overlying encapsulation layers to define the optical cavity regions. This simplifies the deposition process while maintaining precise color control.

Inventive Principle:

Principle #13The other way round (Inversion)

3Manufacturing precision

If color filters are used with optical cavity structures, then color control is improved, but light absorption increases and device efficiency decreases

Engineering Contradiction:

Improvecolor controlVSAvoidlight absorption

Core Design Contradiction:

Manufacturing precisionVSLoss of energy

Solution Approach 1:

The invention extracts the color filtering function from separate color filter layers and integrates it directly into the optical cavity structure itself. The cavity's resonant properties inherently filter and enhance specific wavelengths, eliminating the need for additional color filter layers that would absorb light and reduce efficiency.

Inventive Principle:

Principle #2Taking out (Extraction)

4Manufacturing precision

If vacuum deposition through metal shadow-masks is used for patterned organic material deposition, then optical cavity formation is achieved, but scalability to large substrates becomes difficult

Engineering Contradiction:

Improveoptical cavity formationVSAvoidscalability to large substrates

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The invention replaces the mechanical shadow-mask system with a direct patterning approach using photolithography or self-aligned patterning techniques. This substitution enables deposition of optical cavity structures on large-area substrates without the scalability limitations of shadow-masks, while maintaining precise pattern definition.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

The solution enhances light output and reduces angular color change, achieving efficient and consistent color representation across viewing angles while minimizing manufacturing costs by using unpatterned materials and optimizing microcavity structures.

Implementation Method 1

increasing light output through constructive interference

Methodology Applied

Scientific EffectConstructive interference: Interference

Implementation Method 2

reduces angular color change, achieving efficient and consistent color representation across viewing angles

Methodology Applied

Scientific EffectAngular color dependence reduction: Refraction

Data Source

PatentUS7741770B2LED device having improved light output

Publication Date: 2010.06.22 GLOBAL OLED TECHNOLOGY LLC

AI summary

A light-emitting microcavity diode device includes a reflective electrode and a semi-transparent electrode, formed over a substrate, with an unpatterned light-emitting layer formed between the reflective electrode and the semi-transparent electrode. The reflective electrode, semi-transparent electrode, and unpatterned light-emitting layer form an optical cavity. Either the reflective or semi-transparent electrode is patterned to form independently-controllable, light-emitting sub-pixels. At least one, and fewer than all, of the sub-pixels emit light through a color filter. A first sub-pixel emits light having a first primary color and a second sub-pixel emits a complementary colored light. The light emitted from the first and second sub-pixels changes at one or more different angles. The color of the combined light of the first and second sub-pixels changes less at the one or more different angles than the light from at least one of the first or second sub-pixels. A third sub-pixel emits light through a color filter of a second primary color, different from the first primary color.