Patterned Cathode PLED Light Source for White Emission
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Solution Overview
Problem
Optimizing broad spectrum polymer light-emitting diodes (PLEDs) is challenging due to tight dopant concentration tolerances, undesirable changes in charge transport properties, and stability issues across the operational life of the device, particularly when achieving white emission.
Innovation Solution
A dual emission light source structure with patterned cathodes allows for separate optimization of each PLED emitting different colors, enabling combination for white emission, with options including stacked PLEDs on a common substrate, separate substrates, or physically stacked devices, and patterning methods like laser or Swiss cheese patterns to maximize light output and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a single PLED structure is used for broad spectrum emission, then white emission can be achieved, but dopant concentration tolerances become very tight and charge transport properties deteriorate
Solution Approach 1:
The invention divides the single PLED structure into multiple separate PLEDs, each optimized for a specific emission color (blue, green, red). Each PLED has its own optimized dopant concentration and charge transport properties, eliminating the trade-offs inherent in single-structure broad spectrum devices. The segmented structures are then combined to achieve white emission.
2Illumination intensity
If dopant concentrations are adjusted to change emission color, then color can be tuned, but charge transport properties and device performance deteriorate
Solution Approach 1:
The invention separates the color tuning function from the charge transport function by creating distinct PLEDs for each color. Each PLED maintains its own optimized dopant concentration for both color emission and charge transport, eliminating the adverse effects of dopant concentration adjustments on overall device performance.
3Illumination intensity
If multiple emitters are blended to achieve broad spectrum emission, then white emission can be obtained, but emission stability and reproducibility deteriorate
Solution Approach 1:
The invention replaces the blended emitter approach with segmented PLEDs, where each emitter is contained in a separate, independently optimized device structure. This eliminates the phase separation and stability issues associated with blending multiple emitters, while maintaining broad spectrum emission through spatial combination of the segmented structures.
4Productivity
If patterned cathodes are used to maximize light output, then light transmission and reflection efficiency improve, but device structure complexity increases
Solution Approach 1:
The invention applies patterned cathodes with different local properties (transparent regions for light transmission, reflective regions for light reflection) to optimize light output from each PLED. The patterning creates spatially varying cathode characteristics that maximize overall device performance while managing the increased structural complexity through functional specialization.
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 approach allows for independent optimization of each PLED for maximum efficiency and reliability, maintaining color consistency and enhancing light output by adjusting emission intensity and using transparent or reflective cathode patterns to ensure efficient light transmission and reflection.
Implementation Method 1
A first polymer light emitting diode (PLED) is fabricated on or disposed on one side of a common substrate and emits a first color (spectrum). A second PLED is fabricated on or disposed on an opposite side of the common substrate and emits a second color (spectrum).
Implementation Method 2
The patterned cathodes enable light emission from the PLEDs to combine together
Data Source
AI summary
At least one stacked organic or polymeric light emitting diode (PLEDs) devices to comprise a light source is disclosed. At least one of the PLEDs includes a patterned cathode which has regions which transmit light. The patterned cathodes enable light emission from the PLEDs to combine together. The light source may be top or bottom emitting or both.