Micro Light Emitting Element Tapered Side Surface
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Solution Overview
Problem
Micro light emitting elements suffer from optical crosstalk and low light emission efficiency due to light being absorbed and trapped within the elements, leading to decreased contrast, color purity, and increased power consumption.
Innovation Solution
A micro light emitting element design featuring a compound semiconductor layer with a tapered side surface and a reflective material covering, where the light emission layer is positioned on the light emitting surface, and a transparent insulating film is used between the side surface and the reflective material to enhance light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a compound semiconductor micro light emitting element is used, then high luminance and high durability are achieved, but light extraction efficiency becomes low due to total reflection at the interface between compound semiconductor and outside materials
Solution Approach 1:
The side surface of the micro light emitting element is formed with a tapered shape (curved surface) instead of a flat surface. This curved geometry modifies the incident angles of light at the compound semiconductor interface, reducing total internal reflection and enabling more light to escape, thereby improving light extraction efficiency while maintaining the high luminance characteristics of compound semiconductors
2Productivity
If light is emitted from the side surface of the micro light emitting element, then light can be generated, but optical crosstalk occurs when this light is absorbed and re-emitted by adjacent micro light emitting elements
Solution Approach 1:
The harmful side-emitted light that causes optical crosstalk is extracted and redirected away from adjacent elements through the tapered side surface geometry. The curved surface shape guides this light in specific directions that prevent it from being absorbed by neighboring micro light emitting elements, thereby eliminating the harmful crosstalk effect while preserving useful light generation
Solution Approach 2:
The light that would normally cause harmful optical crosstalk by being absorbed by adjacent elements is converted into a beneficial effect through the tapered surface geometry, which redirects this light away from neighboring elements. The same side-emitted light that poses a problem in conventional flat structures becomes useful by being steered in directions that prevent crosstalk
3Device complexity
If a large amount of light is trapped inside the micro light emitting element due to total reflection, then light emission efficiency decreases, but the structural simplicity is maintained
Solution Approach 1:
The tapered side surface with curved geometry modifies the optical path of light inside the micro light emitting element. This curvature changes the incident angles at the compound semiconductor interface, reducing total internal reflection without adding complex multi-layer structures or additional components, thereby improving light emission efficiency while maintaining relative structural simplicity
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 configuration prevents optical crosstalk and improves light extraction efficiency, leading to enhanced light emission efficiency and reduced power consumption.
Implementation Method 1
a first reflective material covering a side surface of the body... A surface of the second electrode and a surface of the first reflective material on the body side are each a reflective surface that reflects visible light
Implementation Method 2
the compound semiconductor constituting the micro light emitting element has a larger refractive index than air and resin and thus total reflection occurs in a range of wide incident angle when light is incident on an interface between the compound semiconductor and the outside of the compound semiconductor
Data Source
AI summary
A micro light emitting element includes: a body including a compound semiconductor layer in which a first conductive layer, a light emission layer, and a second conductive layer with a conductive type opposite to a conductive type of the first conductive layer are stacked in order from a light emitting surface side; a first electrode including a transparent electrode on the light emitting surface side; a second electrode including a metal film on a side opposite to the light emitting surface side; and a first reflective material covering a side surface of the body. The light emission layer is disposed on the light emitting surface side of the body. The side surface of the body is tapered at an inclination angle to open in a light emitting direction.