Dual-Sided Pixel Layout Blocking Quantum Dot PL in Displays
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Solution Overview
Problem
The existing light-emitting device of a transmissive type cannot display information on both surfaces and suffers from unwanted photo luminescence (PL) light emission due to background light, especially in subpixels using quantum dots for red and green light emission.
Innovation Solution
A light-emitting device with a configuration that includes five subpixels per pixel, where each subpixel has a specific opaque and light-emitting layer arrangement to emit red, green, and blue light on both display surfaces without PL emission, utilizing quantum dots and reflective electrodes to manage light emission directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the background of each pixel is made transparent to enable transmissive-type light emission, then the device can transmit background light, but subpixels with quantum dots are excited by background light and emit unwanted red or green light through photo luminescence
Solution Approach 1:
The pixel is divided into five subpixels with different configurations: first and second subpixels have opaque layers on one side to block background light and prevent PL emission, third and fourth subpixels have opaque layers on the other side, while the fifth subpixel has no opaque layer to transmit background light. This segmentation allows selective background light transmission while preventing unwanted excitation of quantum dots in specific subpixels
Solution Approach 2:
Different subpixels within the same pixel have different optical properties (transparent or opaque) depending on their specific function. The opaque layers are selectively placed only where needed to block background light from reaching quantum dots, while other regions remain transparent to allow background light transmission, creating local quality variations to solve the contradiction
2Object-generated harmful factors
If opaque layers are added to prevent photo luminescence in some subpixels, then unwanted PL emission is suppressed, but the device cannot display information on both surfaces
Solution Approach 1:
The pixel is divided into five subpixels with different configurations: first and second subpixels have opaque layers on one side to block background light and prevent PL emission, third and fourth subpixels have opaque layers on the other side, while the fifth subpixel has no opaque layer to transmit background light. This segmentation allows selective background light transmission while preventing unwanted excitation of quantum dots in specific subpixels
Solution Approach 2:
Each subpixel serves multiple functions: blocking background light, emitting light in specific directions, and preventing unwanted PL emission. The combination of five subpixels with different opaque layer configurations enables the device to achieve both one-sided and two-sided display capabilities while controlling PL emission in different viewing directions
3Illumination intensity
If quantum dots are used in red and green subpixels for light emission, then color display capability is improved, but unwanted PL emission occurs when exposed to background light
Solution Approach 1:
Opaque layers are placed in front of quantum dot-containing subpixels before background light can reach them, preemptively blocking the harmful excitation. This preliminary protective action prevents the quantum dots from being excited by background light, thereby preventing unwanted PL emission while preserving the desired light emission capability when actively driven
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 device effectively displays information on both surfaces without unwanted PL light emission, maintaining color balance and efficiency in light emission.
Implementation Method 1
a first light-emitting layer disposed on the first display surface side relative to the first opaque layer and including a first quantum dot, and emits first color light having a longer wavelength than blue light at the first display surface side
Implementation Method 2
a second light-emitting layer disposed on the second display surface side relative to the second opaque layer and including a second quantum dot, and emits the first color light at the second display surface side
Implementation Method 3
a third light-emitting layer disposed on the first display surface side relative to the third opaque layer and including a third quantum dot, and emits second color light having a longer wavelength than blue light and being different from the first color light at the first display surface side
Implementation Method 4
a fourth light-emitting layer disposed on the second display surface side relative to the fourth opaque layer and including a fourth quantum dot, and emits the second color light at the first display surface side
Implementation Method 5
a fifth subpixel that includes a fifth light-emitting layer and emits the blue light at both the first display surface side and the second display surface side
Data Source
AI summary
A pixel includes a first R subpixel having a reflective electrode disposed on a second display surface side and a first R light-emitting layer disposed on a first display surface side relative to the reflective electrode; a second R subpixel having a reflective electrodes disposed on the first display surface side and a second R light-emitting layer disposed on the second display surface side relative to the reflective electrode; a first G subpixel having a reflective electrode disposed on the second display surface side and a first G light-emitting layer disposed on the first display surface side relative to the reflective electrode; a second G subpixel having a reflective electrode disposed on the first display surface side and a second G light-emitting layer disposed on the second display surface side relative to the reflective electrode; and a B subpixel having a B light-emitting layer.