Photodiode Reflective Layer for OLED Luminance Control
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Solution Overview
Problem
Organic light emitting displays face issues with deteriorating organic material characteristics leading to low luminance and reduced contrast due to external light reflection, and the light-receiving efficiency of photodiodes decreases as devices become smaller and thinner.
Innovation Solution
A method of manufacturing an organic light emitting display that includes a photodiode with a reflective layer providing high reflectivity and a semiconductor layer with defect sites formed by dry etching, which enhances light receiving efficiency and allows for uniform luminance control by adjusting voltage based on incident light intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the organic light emitting display uses a conventional photodiode structure, then the device can detect ambient light, but the light receiving efficiency decreases as devices become smaller and thinner
Solution Approach 1:
The photodiode structure is segmented into distinct functional regions: a first region with high-concentration P and N doping regions for charge generation, and a second region with low-concentration doping for extended light detection. This segmentation allows the photodiode to maintain high light receiving efficiency in a compact form factor by optimizing each region's function separately.
Solution Approach 2:
The photodiode employs a composite doping structure combining high-concentration and low-concentration doped regions within the same semiconductor layer. This composite approach enables the device to achieve both compact size and high light receiving efficiency by leveraging the complementary properties of different doping concentrations in adjacent regions.
2Illumination intensity
If the organic thin film layer is made of organic materials, then the display achieves excellent viewing angle and contrast, but the characteristics deteriorate with time leading to low luminance
Solution Approach 1:
The photodiode serves as a feedback sensor that detects ambient light conditions and operational luminance levels. This feedback mechanism enables the display system to dynamically adjust operating parameters to compensate for organic material deterioration over time, maintaining stable luminance output despite aging effects.
Solution Approach 2:
The display system utilizes parameter changes in the photodiode's electrical characteristics as it detects light. By monitoring these parameter changes and adjusting driving voltages or current levels accordingly, the system compensates for organic material degradation and maintains consistent luminance performance over extended operational periods.
3Reliability
If the display structure includes additional layers for improved light receiving, then the photodiode efficiency increases, but the device complexity increases
Solution Approach 1:
The semiconductor layer serves multiple functions: it acts as the active photodetector element, provides structural support, and enables both high-concentration and low-concentration doping regions within a single layer. This multi-functionality reduces device complexity by eliminating the need for separate structural components while maintaining enhanced light receiving efficiency.
Solution Approach 2:
The invention merges the light detection function and charge generation function into a single integrated photodiode structure with combined doping regions. This consolidation achieves improved light receiving efficiency without increasing overall device complexity by combining multiple functions into one unified component.
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 method improves light receiving efficiency and maintains uniform luminance by reflecting external light back onto the photodiode, compensating for luminance decreases due to aging and ambient light conditions, while maintaining high reflectivity and efficient light emission.
Implementation Method 1
a reflective layer between an upper surface of the substrate and a lower surface of the photodiode... the reflective layer is adapted to provide a reflectivity of light emitted by the organic diode of more than 10%, more preferably more than 30%, more preferably more than 50% and still more preferably more than 70%. Preferably the photodiode reflects light incident from an exterior of the organic light emitting diode onto the photodiode
Implementation Method 2
a light receiver in which a defect site is formed by subjecting the light receiver to a dry etching process
Implementation Method 3
a controller for uniformly controlling luminance of the light emitted from the organic light emitting diode by controlling a voltage, applied to the first electrode and the second electrode, according to the voltage outputted from the photodiode
Data Source
Figure 1~2
Figure 3A~3B
Figure 3C~4B
AI summary
An organic light emitting display includes an organic light emitting diode formed on a substrate, coupled to a transistor; a photodiode formed on the substrate and including a semiconductor layer including a high-concentration P doping region, an intrinsic region with defects and a high-concentration N doping region; and a controller that uniformly controls the luminance of light emitted from the organic light emitting diode by controlling a voltage applied to the first electrode and the second electrode according to the voltage outputted from the photodiode.