OLED Charge Generation Unit for Automotive Red Light Emission
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Solution Overview
Problem
Automotive light emitting devices based on organic light emitting diodes (OLEDs) are not suitable for automotive rear light applications due to their broad visible emission spectrum, which shifts the perceived color towards the yellow part of the spectrum, rather than the deep red, due to human eye spectral sensitivity.
Innovation Solution
A red light emitting device with a stack configuration including a first electrode, an organic light emitting diode, a charge generation unit with an absorbing layer that shifts the light emission towards a longer wavelength within the red spectrum, and a second electrode, where the charge generation unit comprises a diffusion barrier layer to reduce atom/molecule diffusion and enhance temperature stability, using materials like pentacene, rubrene, and metal organic materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If organic light emitting diodes are used to provide red light emission, then the device can emit within the red part of the spectrum, but the effective color points shift towards yellow due to broad emission spectrum and human eye spectral sensitivity
Solution Approach 1:
A charge generation unit is introduced as an intermediary component between the organic light emitting diode and the external environment. This unit contains an absorbing layer that selectively absorbs certain wavelengths and re-emits at deeper red wavelengths, mediating the broad emission spectrum to achieve precise color control in the red range (620-630 nm).
Solution Approach 2:
The patent changes the spectral parameters by introducing materials with specific absorption and emission characteristics. The absorbing layer is selected to have absorption at wavelengths shorter than the emission peak and re-emission at deeper red wavelengths, thereby transforming the broad emission spectrum into a controlled narrow-band red emission that matches automotive lighting requirements.
2Temperature
If the light emitting device operates at high temperatures typical of automotive environments, then the device must maintain functionality, but temperature causes atom and molecule diffusion that degrades performance
Solution Approach 1:
A diffusion barrier layer is introduced as a protective intermediary between the charge generation unit and the organic light emitting diode. This barrier layer prevents thermal diffusion of atoms and molecules from the charge generation unit into the organic diode, thereby protecting the device from temperature-induced degradation while allowing the device to operate in high-temperature automotive environments.
Solution Approach 2:
The diffusion barrier layer provides beforehand protection against thermal diffusion damage. By placing this protective layer in advance, the patent prevents potential degradation from occurring, cushioning the organic light emitting diode against the harmful effects of high-temperature operation before damage can occur.
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 provides a light emitting device with increased red light intensity and improved temperature stability, ensuring correct emission color within the red wavelength range, suitable for automotive rear lights, even at high temperatures, and extends the device's lifetime.
Implementation Method 1
the charge generation unit comprises an absorbing layer having an absorption shifting the light emitted by the light emitting device towards a longer wavelength within the red part of the spectrum
Implementation Method 2
a light emitting device for emitting light is presented, wherein the light emitting device comprises a stack including a first electrode, an organic light emitting diode
Data Source
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AI summary
The invention relates to a light emitting device for emitting light, wherein the light emitting device (1) comprises a stack including a first electrode (16), an organic light emitting diode (17), a charge generation unit (18) and a second electrode (2) , wherein the organic light emitting diode and the charge generation unit are arranged in between the first and second electrodes and wherein the charge generation unit comprises an absorbing layer (9) having an absorption shifting the light emitted by the light emitting device towards a longer wavelength within the red part of the spectrum. Due to the shift towards a longer wavelength within the red part of the spectrum, the light emitting device is better usable in automotive applications. For instance, the light emitting device can be used in a rear light of a vehicle.