OLED Buffer Layer Mitigates Interface Quenching
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Solution Overview
Problem
Quenching effects at the interface between fluorescent and phosphorescent material layers in organic electro-luminescent devices reduce OLED brightness and efficiency, making it difficult to improve device performance.
Innovation Solution
Incorporating a nondoped organic material layer with a highest occupied molecular orbital (HOMO) energy level no higher than that of the host material in the phosphorescent emissive layer, acting as a buffer between the fluorescent and phosphorescent emissive layers to mitigate quenching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fluorescent material layer and phosphorescent material layer are directly adjacent in an organic electro-luminescent device, then the device structure is simple, but quenching occurs at the interface reducing brightness and efficiency
Solution Approach 1:
A nondoped organic material layer is introduced as an intermediary between the fluorescent emissive layer and phosphorescent emissive layer. This intermediate layer has a HOMO energy level no higher than that of the host material in the phosphorescent emissive layer, which prevents electron-hole recombination at the interface and eliminates the quenching effect, thereby improving device efficiency without significantly increasing structural complexity
Solution Approach 2:
The HOMO energy level of the intermediate layer is specifically controlled to be no higher than that of the phosphorescent host material. By adjusting this energy level parameter, the patent prevents charge carrier accumulation and recombination at the interface, thereby resolving the quenching problem while maintaining a relatively simple device structure
2Device complexity
If the HOMO energy level of the intermediate layer is higher than the phosphorescent host material, then the device structure is simpler, but electron-hole recombination occurs at the interface reducing current efficiency
Solution Approach 1:
The patent specifically controls the HOMO energy level parameter of the intermediate layer to be no higher than that of the phosphorescent host material. This parameter adjustment prevents electron-hole recombination at the interface, thereby improving current efficiency while maintaining a relatively simple layered structure
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 nondoped organic material layer effectively reduces quenching, enhancing the current efficiency of the organic electro-luminescent device without altering the original light-emitting color, as shown by improved current efficiency and brightness curves.
Implementation Method 1
quenching may occur at the interface between the fluorescent material layer and the phosphorescent material layer, reducing the OLED brightness
Implementation Method 2
The nondoped organic material layer has a highest occupied molecular orbital (HOMO) energy level no higher than that of the host material in the phosphorescent emissive layer
Implementation Method 3
When an electrical potential difference is applied between the anode and the cathode, electrons are injected into the electron transport layer from the cathode and pass through the electron transport layer and the light emissive layer. At the same time, holes are injected into the hole transport layer from the anode and pass therethrough. The injected electrons and holes are recombined at the interface of the light emissive layer and the hole transport layer, releasing energy as light.
Data Source
AI summary
An organic electro-luminescent device. The device comprises two electrodes and an organic electro-luminescent structure interposed therebetween. The electrodes are disposed on a substrate, one serving as an anode and the other as a cathode. The organic electro-luminescent structure comprises a fluorescent emissive layer, a phosphorescent emissive layer and a nondoped organic material layer interposed therebetween. The phosphorescent emissive layer has a host material. The nondoped organic material layer has a highest occupied molecular orbital (HOMO) energy level no higher than that of the host material in the phosphorescent emissive layer.