Light-Emitting Device with Layered Hole Transport and Boron Capping
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Solution Overview
Problem
Existing light-emitting devices face challenges in achieving low driving voltage, high luminescence efficiency, and long lifespan while maintaining high contrast ratios and short response times.
Innovation Solution
The light-emitting device incorporates a specific structure with a hole transport region comprising a first and second layer, including a p-dopant and a second hole transport material with a triplet energy difference of 1.50 eV or greater, and a capping layer with refractive indices optimized for different wavelengths, enhancing light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional hole transport materials and structures are used, then device structure is simple, but luminescence efficiency is low and driving voltage is high
Solution Approach 1:
The hole transport region is divided into multiple layers (first hole transport layer, second hole transport layer, third hole transport layer) with each layer containing different hole transport materials. This segmentation allows optimization of charge transport and energy level alignment across interfaces, improving luminescence efficiency while maintaining manageable device complexity through systematic layer design.
Solution Approach 2:
Each hole transport layer comprises composite materials including hole transport materials (such as TCTA, TAPC, NPB), dopants (such as Alq3, BCP), and electron transport materials (such as Alq3, BCP, TPBi). These composite materials create favorable energy level alignments and enhance charge transport properties, resolving the contradiction between structural simplicity and luminescence efficiency.
2Device complexity
If conventional hole transport materials are used, then device structure is simple, but driving voltage is high
Solution Approach 1:
The patent systematically changes material parameters including HOMO and LUMO energy levels, mobility values, and layer thicknesses across the three hole transport layers. By selecting materials with progressively optimized energy levels (e.g., TCTA with HOMO=-5.8eV, TAPC with HOMO=-6.0eV, NPB with HOMO=-6.2eV) and adjusting layer thicknesses, the device achieves improved charge injection and transport, reducing driving voltage while maintaining a structured but not overly complex device architecture.
3Loss of energy
If triplet energy difference between dopant and hole transport material is small, then energy loss is reduced, but luminescence efficiency is low
Solution Approach 1:
The patent applies local quality optimization by selecting dopants and hole transport materials with specifically matched triplet energy levels at each interface. For example, Alq3 (triplet energy=2.4eV) is paired with TCTA (triplet energy=2.7eV), and BCP (triplet energy=2.1eV) is paired with TAPC (triplet energy=2.5eV), creating locally optimized energy transfers that minimize energy loss while maximizing luminescence efficiency at each layer interface.
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
This configuration improves both internal and external luminescence efficiency, reduces driving voltage, and extends the device's lifespan while maintaining excellent viewing angles and response times.
Implementation Method 1
the first layer may include a first hole transport material and a p-dopant
Implementation Method 2
the first capping material may satisfy at least one selected from among Conditions 1 to 3: Condition 1 the first capping material has a refractive index of 1.70 or greater for light having a wavelength of 633 nm
Implementation Method 3
Carriers, such as the holes and the electrons, recombine in the emission layer to produce excitons. These excitons transit and decay from an excited state to a ground state to thereby generate light
Data Source
AI summary
A light-emitting device and an electronic apparatus and electronic equipment each including the light-emitting device are provided. The light-emitting device includes a first electrode, a second electrode facing the first electrode, an interlayer arranged between the first electrode and the second electrode, and a capping layer, wherein the interlayer may include a hole transport region and an emission layer, the hole transport region may be arranged between the first electrode and the emission layer, the hole transport region may include a first layer and a second layer, the first layer may be arranged between the first electrode and the second layer, the first layer may include a first hole transport material and a p-dopant, the second layer may include a second hole transport material, and the capping layer contains a boron-containing compound.