Parallel Dual p-n Junction LED for High Flux at Low Voltage
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Solution Overview
Problem
Green LEDs face efficiency droop issues due to increased non-radiative Auger recombination at higher current densities, and existing cascade LED designs require high operating voltages, limiting their application in small optical source systems.
Innovation Solution
The development of LED devices with a first and second p-n junction deposited sequentially on the same wafer, where one light-emitting active region is embedded between the n- and p-layers of each junction, allowing for parallel current passage with a single voltage source, reducing voltage requirements and enhancing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If current density is increased to match the flux of conventional LEDs, then light output is improved, but efficiency drops due to non-radiative Auger recombination
Solution Approach 1:
The LED device is segmented into multiple p-n junctions (first and second junctions) with separate light-emitting active regions. Each junction operates at lower current density while collectively providing high light output, thus avoiding Auger recombination losses that occur in single high-current-density LEDs
2Loss of energy
If cascade LED design with multiple p-n junctions in series is used to reduce current density, then efficiency is improved, but operating voltage increases beyond acceptable limits
Solution Approach 1:
Instead of connecting multiple p-n junctions in series (cascade configuration) which increases voltage, the patent inverts the approach by connecting them in parallel. This allows multiple junctions to operate simultaneously at lower voltage while maintaining high efficiency through reduced current density in each junction
3Illumination intensity
If multiple p-n junctions are connected in series to achieve high flux from small source size, then light output is improved, but operating voltage exceeds 6V limiting applications
Solution Approach 1:
The high flux requirement is met by segmenting the LED into multiple parallel p-n junctions, each contributing to the total light output. This segmentation allows the system to achieve high flux without concentrating all current through a single high-voltage junction
Solution Approach 2:
The patent inverts the conventional series connection approach by using parallel connection of multiple p-n junctions. This inversion maintains high flux output while keeping operating voltage within acceptable limits for existing illumination systems
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 operates at lower voltages with higher optical flux and efficiency compared to standard LEDs, making it suitable for applications requiring reduced current density without increasing system costs.
Implementation Method 1
a first n-type layer on a first tunnel junction, the first tunnel junction on a first p-type layer
Data Source
AI summary
Provided is an LED comprised of a first and a second p-n junction deposited sequentially on the same wafer. The first and second junctions have opposite orders of deposition of the n- and p-layers. One light-emitting active region is embedded between the n- and p-layers of the first junction and another light-emitting active region is embedded between the n- and p-layers of the second junction. Contacts are processed such that forward current can be passed in parallel through both of the junctions using a single voltage source. For a given forward current, the LED operates at lower voltage with higher optical flux and efficiency.