Conversion Element Quantum Well Optical Pumping Spectral Control

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Solution Overview

Problem

Existing conversion elements for generating colored light, such as green or red light, face inefficiencies due to high forward voltage, sub-linear light-current dependence, and poor charge carrier confinement, leading to reduced efficiency and broad spectral emission, which is undesirable for applications requiring good color rendering.

Innovation Solution

A conversion element with an active region formed from semiconductor material comprising multiple barriers and quantum wells, combined with input and output coupling structures, where the active region is positioned between structural elements on the top side and additional structural elements on the side facing away, enhancing the probability of electromagnetic radiation emission and entry, thereby increasing efficiency and narrowing the spectral width.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If optical pumping is used to generate colored light in conversion elements, then efficiency can be improved, but the spectral width becomes too broad for applications requiring good color rendering

Engineering Contradiction:

Improveconversion efficiencyVSAvoidspectral width control

Core Design Contradiction:

Use of energy by moving objectVSManufacturing precision

Solution Approach 1:

The conversion element is divided into multiple quantum wells (e.g., 3-5 quantum wells) with different composition ratios of InGaN, each emitting at slightly different wavelengths. This segmentation of the emission spectrum allows for high efficiency while controlling the overall spectral width to achieve good color rendering properties.

Inventive Principle:

Principle #1Segmentation

2Manufacturing precision

If direct green light-generating InGaN-based LEDs are used, then color rendering can be achieved, but efficiency is reduced due to high forward voltage and poor charge carrier confinement

Engineering Contradiction:

Improvecolor rendering qualityVSAvoidconversion efficiency

Core Design Contradiction:

Manufacturing precisionVSUse of energy by moving object

Solution Approach 1:

Instead of directly injecting charge carriers into the active region (which causes high forward voltage and poor confinement), the patent uses optical pumping as an intermediary method. Blue or UV light pumps the InGaN quantum wells, generating electron-hole pairs that recombine to emit green light. This indirect approach achieves high efficiency while maintaining good color rendering.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Power

If electrical charge carrier injection is used, then light generation can occur, but efficiency is reduced due to sub-linear light-current dependence and charge carrier loss

Engineering Contradiction:

Improvelight generation capabilityVSAvoidconversion efficiency

Core Design Contradiction:

PowerVSUse of energy by moving object

Solution Approach 1:

The patent replaces the electrical injection mechanism (mechanical/electrical system) with optical pumping (optical system). Instead of injecting charge carriers electrically, blue or UV light is used to excite the quantum wells, which then emit green light through photoluminescence. This substitution eliminates the sub-linear light-current dependence and charge carrier loss associated with electrical injection.

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 described configuration significantly increases efficiency by over 30% compared to smooth surface conversion elements, achieving high efficiency and a narrow spectral line width, while avoiding electrical charge carrier injection and using optical pumping for improved performance.

Implementation Method 1

a secondary radiation with a longer wavelength than the pump radiation is preferably generated by pumping with a primary radiation

Methodology Applied

Scientific EffectPhotoluminescence: Photoluminescence

Implementation Method 2

The charge carriers are generated by absorption of primary radiation which is of shorter wavelength than the secondary radiation, for example in the barriers

Methodology Applied

Scientific EffectAbsorption of electromagnetic radiation: Absorption (EM radiation)

Data Source

PatentUS11557698B2Conversion element and radiation-emitting semiconductor device comprising a conversion element of said type

Publication Date: 2023.01.17 OSRAM OLED

AI summary

Disclosed is a conversion element (1) comprising an active region (13) that is formed by a semiconductor material and includes a plurality of barriers (131) and quantum troughs (132), a plurality of first structural elements (14) on a top face (la) of the conversion element (1), and a plurality of second structural elements (15) and/or third structural elements (16) which are arranged on a face of the active region (13) facing away from the plurality of first structural elements (14). Also disclosed is a method for producing a conversion element of said type.