DBR Optical Filter for LED Color Conversion and Cross-Talk Reduction
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Solution Overview
Problem
Existing LED technologies face challenges in creating multi-coloured displays using single-colour LEDs due to low absorption coefficients of phosphors, pixel-pixel cross-talk, and instability of colour-conversion quantum dots, particularly in high-density LED wafer processing.
Innovation Solution
An optical filter with a Distributed Bragg Reflector (DBR) and a porous layer coated with colour-conversion material is used to prevent transmission of specific wavelengths, enhancing colour-conversion efficiency and stability by reflecting incident light back into the LEDs for better excitation of quantum dots, thereby reducing cross-talk and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If phosphors are used to convert blue LED light to other colours, then multi-coloured display is achieved, but the low absorption coefficient requires a thick phosphor layer which causes pixel-pixel cross-talk
Solution Approach 1:
The patent extracts the harmful residual blue light from the optical path by introducing a DBR (Distributed Bragg Reflector) that selectively reflects blue light wavelengths back into the device, preventing them from contributing to cross-talk between pixels while allowing the phosphor conversion to proceed
Solution Approach 2:
The patent applies local quality by using a DBR with specific wavelength-selective properties positioned in the optical path, creating a localized optical filter that affects only blue light wavelengths while leaving other wavelengths unaffected, thereby addressing cross-talk specifically without impacting overall display performance
2Use of energy by moving object
If colour-conversion quantum dots are impregnated into LED structures, then colour conversion efficiency is improved, but stability and reliability problems occur
Solution Approach 1:
The patent introduces a DBR as an intermediary optical element that reflects residual blue light back into the device, indirectly enhancing quantum dot excitation without requiring direct contact or integration of quantum dots into the LED structure, thereby maintaining quantum dot stability while improving conversion efficiency
3Adaptability or versatility
If electrochemical etching and quantum dot impregnation are performed on high-density LED wafers, then multi-colour pixels are created, but the processing becomes inefficient and challenging
Solution Approach 1:
The patent segments the optical processing approach by applying a DBR structure that can be integrated at the wafer level rather than requiring individual pixel processing, allowing parallel processing of entire wafer areas and significantly improving manufacturing efficiency
Solution Approach 2:
The patent employs preliminary action by integrating the DBR structure into the device architecture before final assembly, enabling the optical filtering and reflection functionality to be established upfront, which simplifies subsequent manufacturing steps and improves overall processing efficiency
4Use of energy by moving object
If a thick phosphor layer is used to compensate for low absorption coefficient, then colour conversion is achieved, but blue light transmission increases causing residual blue light emission
Solution Approach 1:
The patent converts the harmful residual blue light into a beneficial element by using a DBR to reflect it back into the device, where it can be re-absorbed by phosphors or quantum dots for additional colour conversion, thereby turning the harmful blue light leakage into an opportunity for enhanced colour conversion efficiency
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 significantly improves colour-conversion efficiency and stability of quantum dots, reducing blue light leakage and cross-talk, and simplifies processing by integrating the optical filter with monochromatic LEDs to produce RGB pixels without requiring electrochemical treatment of the LEDs themselves.
Implementation Method 1
the first region of the optical filter comprises a Distributed Bragg Reflector (DBR) configured to prevent transmission of light of a predetermined wavelength λ1 out of the LED device
Implementation Method 2
The optical filter is configured to absorb light of wavelength λ1 emitted by the first plurality of LEDs
Implementation Method 3
the colour-conversion material is configured to convert light of wavelength λ1 to light of wavelength λ2
Data Source
AI summary
An LED device comprises a plurality of light-emitting diodes (LEDs), and an optical filter arranged to filter light emitted by the plurality of LEDs. The optical filter comprises a first region arranged to filter light emitted from a first portion of the plurality of LEDs, in which the first region of the optical filter comprises a Distributed Bragg Reflector (DBR) configured to prevent transmission of light of a predetermined wavelength λ1. The LED device may comprise a colour-conversion material positioned between the first portion of the LEDs and the DBR, the colour-conversion material being configured to emit light at one or more wavelengths different from the emission wavelength λ1 of the first portion of LEDs. An optical filter and a method of manufacture are also provided.