White OLED Layer Structure for Warm Light With Low Blue Emission
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Solution Overview
Problem
Existing organic EL elements face challenges in achieving white light emission with low color temperature, high color rendering properties, and reduced melatonin suppression, while maintaining power efficiency and avoiding glare and eye irritation.
Innovation Solution
The organic EL element incorporates a green-red mixed phosphorescent light-emitting layer and a blue fluorescent light-emitting layer, with a hole transporting layer as an adjustment layer to balance spectral intensity, reducing blue emission and enhancing green and red emissions, thereby achieving a low color temperature, high color rendering index, and reduced Melanopic Ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If blue light emission is increased to achieve high color rendering index, then color rendering property is improved, but Melanopic Ratio increases causing melatonin suppression and eye irritation
Solution Approach 1:
The patent changes the spectral parameters by using a green-red mixed phosphorescent light-emitting layer combined with a blue fluorescent light-emitting layer, where the green phosphorescent material has a peak wavelength of 500-580nm and red phosphorescent material has peak wavelength of 590-680nm. This parameter configuration achieves high color rendering index (Ra≥80) while controlling blue light emission to maintain Melanopic Ratio ≤0.65, thus resolving the contradiction between color rendering and melatonin suppression.
Solution Approach 2:
The patent employs composite light-emitting materials including green phosphorescent material, red phosphorescent material, and blue fluorescent material in specific layers. The green red mixed phosphorescent light-emitting layer contains both green and red phosphorescent materials that work together to emit green and red light, while the blue fluorescent light-emitting layer emits blue light. This composite material approach balances the spectrum to achieve high color rendering without excessive blue light emission.
2Object-affected harmful factors
If blue light emission is reduced to lower Melanopic Ratio, then melatonin suppression is reduced, but color rendering index deteriorates
Solution Approach 1:
The patent optimizes the peak wavelengths of the phosphorescent and fluorescent materials: green phosphorescent material (500-580nm), red phosphorescent material (590-680nm), and blue fluorescent material (440-480nm). By carefully selecting these parameters and controlling their intensity ratios, the patent achieves adequate color rendering (Ra≥80) while limiting blue light emission to maintain Melanopic Ratio ≤0.65.
Solution Approach 2:
The patent applies different light-emitting materials with specific properties to different layers: the green red mixed phosphorescent light-emitting layer is positioned to emit green and red light, while the blue fluorescent light-emitting layer is positioned to emit blue light. This local differentiation of material properties allows each layer to contribute optimally to the overall spectral balance, achieving high color rendering without excessive blue light.
3Temperature
If green and red light emission is enhanced to achieve low color temperature, then color temperature is reduced, but blue light emission must be suppressed
Solution Approach 1:
The patent configures the peak wavelengths of the light-emitting materials to produce a spectral distribution with enhanced green (500-580nm) and red (590-680nm) regions while controlling blue (440-480nm) region. This parameter optimization achieves low color temperature (2200-3000K) by intensifying the green and red emissions relative to blue, thereby reducing the overall color temperature while limiting harmful blue light emission to maintain Melanopic Ratio ≤0.65.
4Ease of manufacture
If white light with high color rendering is achieved using conventional methods, then color rendering index is improved, but power efficiency deteriorates
Solution Approach 1:
The patent uses phosphorescent materials with high quantum efficiency: green phosphorescent material with peak wavelength 500-580nm and red phosphorescent material with peak wavelength 590-680nm in the green red mixed phosphorescent light-emitting layer, combined with blue fluorescent material with peak wavelength 440-480nm. These high-efficiency phosphorescent and fluorescent materials convert electrical energy to light energy efficiently while producing the desired spectral distribution for high color rendering index (Ra≥80).
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 results in white light with a correlated color temperature of 2200 K to 3000 K, a Melanopic Ratio of 0.65 or less, and a color rendering index of 80 or more, providing gentle illumination that reduces eye strain and promotes better sleep quality.
Implementation Method 1
An organic EL element is a semiconductor element that converts electric energy into light energy
Implementation Method 2
the green red light emitting unit including a green red mixed phosphorescent light-emitting layer that includes: a green phosphorescent material; a red phosphorescent material
Implementation Method 3
the blue light emitting unit including: a blue fluorescent light-emitting layer that emits blue light when energized
Data Source
AI summary
An organic electroluminescent element capable of emitting white light having a low color temperature and high color rendering properties with practical power efficiency includes a light-pervious substrate, a light-pervious anode layer, a light-emitting functional layer, and a metal cathode layer. The functional layer includes a green red light emitting unit, a unit connection mechanism, and a blue light emitting unit. The green red light emitting unit includes a green red mixed phosphorescent light-emitting layer containing a host material for a phosphorescent light-emitting layer, and the blue light emitting unit includes a hole transport adjustment layer adjacent to a blue fluorescent light-emitting layer on a side of the unit connection mechanism. White light can be emitted from the light emission surface with a correlated color temperature TCP of 2200 K to 3000 K and a color rendering property Ra of 80 or more.