Nanowire LED Luminance Control via Integrated Photodiode Feedback
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Solution Overview
Problem
LEDs with discrete nanowire elements face variability in luminance performance over time, making them unreliable, due to factors like random nucleation mechanisms and inhomogeneities in growth techniques such as MBE and MOCVD.
Innovation Solution
An electroluminescent device with integrated photodiode sensors that regulate luminance by controlling the voltage of primary nanowires based on photocurrent generated by secondary nanowires, using a comparator circuit to adjust the forward voltage and ensure constant light power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If nanowires are produced using MBE or MOCVD growth techniques, then the emission surface area is increased, but inhomogeneities and random nucleation mechanisms cause variability in luminance performance
Solution Approach 1:
The patent implements a feedback control system where photodiodes integrated on the same substrate as the nanowire LEDs detect the actual light emission, and this detection signal is used to adjust the drive current to maintain constant luminance output despite manufacturing inhomogeneities
Solution Approach 2:
The system uses self-measurement and self-regulation where the LED array's own emission is detected by integrated photodiodes, and the system automatically adjusts its operating parameters without external intervention to maintain performance consistency
2Device complexity
If discrete nanowire elements are used, then the device complexity is reduced, but luminance variability over time increases
Solution Approach 1:
The patent combines multiple functions into a single integrated structure: nanowire LEDs for light emission, photodiodes for light detection, and control circuitry for regulation, all fabricated on the same substrate to create a self-regulating system that maintains luminance stability without complex external components
3Reliability
If integrated photodiode sensors are added to regulate luminance, then luminance stability is improved, but device complexity increases
Solution Approach 1:
The nanowire structure serves dual functions: it can operate as an LED for light emission when forward-biased, and as a photodiode for light detection when reverse-biased. This multi-functionality allows the same physical structure to perform both emission and sensing roles, reducing the need for separate dedicated sensor elements
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 stabilizes luminance performance by using photocurrent feedback to regulate the electroluminescent device, reducing variability and maintaining consistent light output despite environmental changes or manufacturing inhomogeneities.
Implementation Method 1
a second series of secondary so-called detection nanowires adjacent to said primary nanowires, connected to second electrical contacts and capable of generating a photocurrent under the action of an ambient light and/or of a portion of the light emitted by some of said primary nanowires
Implementation Method 2
a first series of so-called emission primary nanowires comprising nanowires connected to first electrical contacts and capable of emitting light under the action of a so-called forward first voltage
Data Source
AI summary
An electroluminescent device comprises a structure comprising a set of nanowires on the surface of a substrate, comprising: a first series of primary so-called emission nanowires (NTie) comprising nanowires connected to first electrical contacts and capable of emitting light under the action of a forward first voltage from a forward voltage or current source; a second series of secondary detection nanowires (NTid) adjacent to the primary nanowires, connected to second electrical contacts and capable of generating a photocurrent under the action of an ambient light and/or of a portion of the light emitted by some of the primary nanowires, under the control of a second reverse voltage, from a voltage or current source; means for controlling the forward voltage as a function of the photocurrent. A method for controlling the luminance of an electroluminescent device is provided.