Parallel Dual-Junction LED Structure 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 with multiple p-n junctions in series result in high operating voltage, limiting their application in low-voltage 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 multiple p-n junctions are stacked in series (cascade LED), then light output flux is increased, but operating voltage becomes too high (>6V)
Solution Approach 1:
The LED structure is segmented into multiple independent light-emitting stacks (first light emitting stack, second light emitting stack), each containing its own p-n junction with light-emitting active region. These stacks are connected in parallel rather than series, allowing each segment to contribute to total light output while maintaining lower individual voltage requirements.
Solution Approach 2:
Instead of connecting multiple p-n junctions in series (cascade configuration) to increase flux, the patent inverts the approach by connecting them in parallel. This reversal of the conventional cascade architecture allows high flux output to be achieved without the compounding voltage increase that occurs in series connections.
2Illumination intensity
If current density is increased to match conventional LED flux, then light output is sufficient, but efficiency droop increases due to Auger recombination
Solution Approach 1:
The total current load is segmented across multiple parallel p-n junctions (first p-n junction, second p-n junction). Each junction operates at lower current density while contributing to the overall light output, thereby avoiding the efficiency droop and Auger recombination losses that occur when a single junction operates at high current density.
Solution Approach 2:
Multiple light-emitting active regions (first light-emitting active region, second light-emitting active region) are merged in parallel to achieve high total flux output. The combined light output of multiple efficient, low-current-density junctions exceeds that of a single high-current-density junction, eliminating efficiency droop while maintaining high illumination intensity.
3Device complexity
If single p-n junction is used, then device complexity is low, but cannot achieve high flux without high current density
Solution Approach 1:
Multiple p-n junctions with light-emitting active regions are merged in parallel within a single integrated device structure. This combination allows the device to achieve high flux output comparable to conventional high-power LEDs while operating at lower current densities and reduced voltage, without requiring complex external optical systems or multiple separate components.
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 proposed LED design operates at lower voltage with higher optical flux and efficiency compared to standard LEDs, addressing the efficiency droop and high voltage issues of existing designs, while maintaining comparable light output.
Implementation Method 1
A light emitting diode (LED) is a semiconductor light source that emits visible light when current flows through it
Implementation Method 2
the first p-type layer on a first tunnel junction, the second light emitting stack comprises a second n-type layer in contact with the first tunnel junction and on a second tunnel junction
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.