LED Cell Layout With Current Blocking to Suppress Droop
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Solution Overview
Problem
Light emitting diodes (LEDs) face a decrease in external quantum efficiency and luminous efficacy due to the droop phenomenon when current density increases, limiting their performance in high current applications.
Innovation Solution
A light emitting diode design featuring a substrate with first to fourth light emitting cells connected in series and parallel configurations, along with current blocking layers, to reduce current density and prevent current crowding, thereby improving luminous efficacy and suppressing the droop phenomenon.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If current density is increased to improve light output intensity, then luminous output increases, but external quantum efficiency decreases due to droop phenomenon
Solution Approach 1:
The LED structure is segmented into multiple light emitting cells (first to fourth cells) with separate lower semiconductor layers. This segmentation allows current to be distributed across multiple independent regions, reducing current density in each cell and mitigating the droop phenomenon while maintaining high overall light output intensity.
Solution Approach 2:
Current blocking layers are strategically positioned at specific locations (between light emitting cells and at electrode pad interfaces) to control current distribution locally. This creates non-uniform current density distribution that prevents current crowding at critical interfaces while maintaining efficient carrier injection in active regions.
2Productivity
If current density is increased to improve luminous efficacy, then light output increases, but droop phenomenon causes light loss
Solution Approach 1:
By dividing the LED into multiple light emitting cells with independent lower semiconductor layers, the total current is distributed across multiple paths. This reduces the current density in each individual cell, suppressing droop and minimizing light loss while maintaining high luminous efficacy through the combined output of all cells.
Solution Approach 2:
Current blocking layers act as intermediary elements that regulate current flow between electrode pads and lower semiconductor layers. These layers prevent excessive current concentration at interfaces, reducing droop-induced light loss and improving overall luminous efficacy by optimizing current distribution.
3Power
If multiple light emitting cells are connected to increase output, then light output increases, but connecting portions may disconnect under high current
Solution Approach 1:
Current blocking layers are positioned at critical connecting portions between light emitting cells and at electrode pad interfaces. This local modification creates regions with controlled electrical properties that reduce current concentration and stress at these vulnerable connection points, preventing disconnection while allowing high overall power output.
4Power
If current is concentrated at electrode pads to improve electrical connection, then electrical conductivity increases, but current crowding occurs reducing efficiency
Solution Approach 1:
Current blocking layers are strategically positioned between electrode pads and lower semiconductor layers, and between light emitting cells. These layers create localized regions that control current distribution, preventing current crowding at electrode pad interfaces while maintaining good electrical connection. This optimizes both electrical conductivity and reduces energy loss from current concentration.
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 design allows for improved luminous efficacy by reducing current density and uniform current spreading, enhancing the LEDs' performance under high current conditions while minimizing light loss and preventing disconnection.
Implementation Method 1
A light emitting diode (LED) refers to a solid state light emitting device that converts electrical energy into light
Data Source
AI summary
A light emitting diode including a substrate having a first area and a second area defined by an isolation groove line, a semiconductor stack disposed on the substrate and including a lower semiconductor layer, an upper semiconductor layer, an active layer, a first electrode pad electrically connected to the lower semiconductor layer, a second electrode pad electrically connected to the upper semiconductor layer, and a connecting portion electrically connecting the semiconductor stack disposed in the first and second areas to each other, and including a first portion, a second portion, and a third portion extending from a second distal end of the first portion, in which the isolation groove line is disposed between the first and second electrode pads and exposes the substrate, the first portion extends along a first direction substantially parallel to an extending direction of the isolation groove line, and the second and third portions extend in a second direction crossing the first direction.