LED Light Extraction via Block Copolymer Phase Separation
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Solution Overview
Problem
The existing methods for enhancing light extraction efficiency in LEDs using nano-scaled relief structures formed by self-assembly of block copolymers face challenges in achieving complete separation of dot patterns, leading to connected convex portions and reduced light extraction efficiency.
Innovation Solution
A semiconductor light emitting device with a relief structure on its light extraction surface, where 90% or more of the convex portions have a circularity coefficient of 0.7 or higher, formed by varying the equivalent circular diameters and using a method involving block copolymer phase-separation and etching as a mask to ensure high isolation and efficient light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If self-assembly of block copolymers is used to form nano-scaled relief structure, then manufacturing cost is reduced and large area processing is enabled, but dot patterns cannot be completely separated leading to connected convex portions
Solution Approach 1:
The patent changes the chemical composition parameters of the resist material by using a copolymer with specific blocks (styrene and methyl methacrylate) in controlled ratios. This parameter change enables the resist to undergo microphase separation during heat treatment, automatically forming separated dot patterns without requiring expensive lithography equipment, thus resolving the contradiction between manufacturing cost and pattern separation quality
Solution Approach 2:
The patent utilizes the phase transition phenomenon of block copolymers during heat treatment. The copolymer resist undergoes microphase separation when heated to specific temperatures, causing the immiscible polymer blocks to segregate into distinct domains. This phase transition automatically creates well-separated dot patterns, solving the problem of connected convex portions while maintaining low manufacturing cost through self-assembly
2Productivity
If heat treatment time is insufficient, then processing time is reduced, but dot patterns become connected due to insufficient phase separation
Solution Approach 1:
The patent optimizes the thermal parameters by specifying precise heat treatment conditions (temperature range and time duration). These parameter changes ensure that the copolymer undergoes sufficient microphase separation to create completely separated dot patterns, while avoiding excessive processing time. The controlled parameter changes resolve the contradiction between processing speed and separation quality
Solution Approach 2:
The copolymer resist acts as an intermediary material that mediates between the manufacturing process and the final relief structure. Its specific block composition serves as a chemical mediator that facilitates controlled phase separation at optimized temperatures and times, enabling complete dot separation without requiring excessive heat treatment duration, thus resolving the time-quality contradiction
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 achieves a light extraction efficiency of 90% or more by forming a relief structure with high isolation of convex portions, effectively enhancing the diffraction effects and reducing light loss, thereby improving the brightness of LEDs.
Implementation Method 1
forming a resin composition thin film containing a block copolymer on either the semiconductor multilayer film or an inorganic composition thin film used as an intermediate mask layer; causing the resin composition thin film to phase-separate by performing a heat treatment
Implementation Method 2
forming a nano-scaled relief structure on a surface of an LED to prevent the reflection of light at the interface between the LED and air utilizing scattering/diffraction effects
Implementation Method 3
forming a nano-scaled relief structure on a surface of an LED to prevent the reflection of light at the interface between the LED and air utilizing scattering/diffraction effects
Data Source
AI summary
A semiconductor light emitting device including: a substrate; an electrode layer; and a semiconductor multilayer film disposed between the substrate and the electrode layer, the semiconductor multilayer film including: an n-type semiconductor layer; a p-type semiconductor layer; and an active layer disposed between the n-type semiconductor layer and the p-type semiconductor layer, wherein the semiconductor multilayer film has a light extraction surface from which a light emitted in the semiconductor multilayer film is extracted, the light extraction surface being formed with a relief structure having nano-scaled convex portions, wherein the relief structure is formed to have variation in equivalent circular diameters of the convex portions, and wherein 90% or more of the convex portions in the relief structure are configured to have circularity coefficient of (4π×(area)/(circumferential length)2) being equal to or larger than 0.7.