Light-emitting device, light-emitting apparatus, electronic device, and lighting device
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Solution Overview
Problem
Existing organic light-emitting devices (OLEDs) emitting near-infrared light face challenges with low emission efficiency and short lifetimes due to carrier traps and narrow band gap of dopants, limiting their application in biosensing and other areas.
Innovation Solution
Incorporating a first layer with a specific organic compound between electrodes, having a high extinction coefficient and refractive index, to enhance light extraction efficiency and adjust optical path length for improved emission efficiency and lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a near-infrared light-emitting dopant is doped in a light-emitting layer, then near-infrared light emission is achieved, but emission efficiency is reduced due to carrier traps and narrow HOMO-LUMO gap
Solution Approach 1:
The patent introduces a host material as an intermediary between the electrode and the near-infrared dopant. The host material has a wider HOMO-LUMO gap than the dopant, preventing carrier accumulation and trap formation. The host acts as a mediator that transports carriers to the dopant without suffering from the narrow gap problem itself, thereby maintaining high emission efficiency while enabling near-infrared light emission.
2Illumination intensity
If a near-infrared light-emitting dopant is doped in a light-emitting layer, then near-infrared light emission is achieved, but element lifetime is adversely affected due to carrier traps
Solution Approach 1:
The host material serves as a protective intermediary that prevents direct interaction between carriers and the narrow-gap dopant. By having a wider HOMO-LUMO gap, the host material prevents carrier accumulation that would otherwise create traps and degrade the device. This intermediary layer protects the dopant and extends device lifetime while maintaining near-infrared emission capability.
3Device complexity
If conventional light-emitting structures are used, then simple device structure is maintained, but light extraction efficiency is low due to optical path length limitations
Solution Approach 1:
The patent optimizes the optical parameters of the light-emitting layer by carefully selecting the host material with specific refractive index and absorption coefficient. By changing these optical parameters, the light extraction efficiency is improved without adding complex micro-cavity structures or photonic crystals. The host material's optical properties are tuned to maximize light outcoupling in the near-infrared region.
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 a near-infrared OLED with enhanced emission efficiency and reduced power consumption, suitable for biosensing applications.
Implementation Method 1
the first layer has the local maximum value of an extinction coefficient k in a visible light region
Implementation Method 2
Light-emitting devices (organic EL devices) including organic compounds and utilizing electroluminescence (EL) have been put into practical use
Implementation Method 3
the first layer contains an organic compound; and the first layer has the local maximum value of an extinction coefficient k in a visible light region
Data Source
AI summary
A near-infrared organic EL device with favorable efficiency is provided. A light-emitting device including a first electrode, a second electrode, and an EL layer is provided; in which the EL layer is positioned between the first electrode and the second electrode; in which the EL layer emits light having a peak of an emission spectrum in a wavelength range of greater than or equal to 750 nm and less than or equal to 1000 nm; in which one of the first electrode and the second electrode is an electrode having a transmitting property with respect to light with a peak wavelength of the emission spectrum of the EL layer; in which a first layer is provided in contact with a surface of the electrode having a transmitting property, which is opposite to a surface facing the EL layer; in which the first layer contains an organic compound; and in which the first layer has the local maximum value of an extinction coefficient k in the visible light region.