Exciplex Light-Emitting Element for Low Voltage
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Solution Overview
Problem
Existing light-emitting elements with phosphorescent materials face challenges in achieving high emission efficiency and low driving voltage due to difficulties in adjusting carrier balance and reducing the energy difference between singlet and triplet excited states, leading to increased driving voltage.
Innovation Solution
A light-emitting element is designed with a structure that includes a first and second organic compound forming an exciplex, where the LUMO level difference is between 0 eV and 0.5 eV, and a guest material that converts triplet excitation energy into light emission, optimizing carrier transport and reducing driving voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If phosphorescent material is used to convert triplet excited state into light emission, then emission efficiency is improved, but driving voltage increases due to large energy difference between singlet and triplet excited states
Solution Approach 1:
The patent introduces a host material as an intermediary between the electrodes and the phosphorescent guest material. The host material absorbs electrical energy and transfers it to the guest material, mediating the energy conversion process. This allows the system to operate at lower voltages while maintaining high emission efficiency, as the host material's energy levels are optimized to bridge the gap between electrical input and phosphorescent output.
Solution Approach 2:
The patent optimizes the energy level parameters of the host and guest materials to reduce the driving voltage. By carefully selecting materials with appropriate HOMO and LUMO levels, and ensuring the triplet excited state energy of the host is slightly higher than that of the guest, the system achieves efficient energy transfer at lower operating voltages, thus resolving the contradiction between emission efficiency and driving voltage.
2Power
If organic material with favorable carrier transport property is used, then driving voltage is reduced, but it is difficult to adjust carrier balance and achieve high emission efficiency
Solution Approach 1:
The patent employs a composite light-emitting layer consisting of a host material and a phosphorescent guest material. The host material provides excellent carrier transport properties, while the guest material ensures high emission efficiency through phosphorescence. The synergistic combination of these two materials allows the system to achieve both low driving voltage and high emission efficiency simultaneously, resolving the contradiction between these two parameters.
Solution Approach 2:
The patent assigns different functional qualities to different components: the host material is optimized for carrier transport and energy transfer, while the guest material is optimized for light emission. This division of functional quality allows each material to excel at its specific task, with the host material reducing driving voltage through good carrier transport and the guest material ensuring high emission efficiency through phosphorescence.
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 enables high emission efficiency, low power consumption, and reliable light-emitting elements with reduced driving voltage by efficiently exciting phosphorescent materials through exciplex formation and energy transfer.
Implementation Method 1
A light-emitting element is designed with a structure that includes a first and second organic compound forming an exciplex, where the LUMO level difference is between 0 eV and 0.5 eV, and a guest material that converts triplet excitation energy into light emission
Implementation Method 2
light emission from the triplet excited state is referred to as phosphorescence. The statistical generation ratio of the excited states in the light-emitting element is considered to be S*:T*=1:3. In other words, a light-emitting element formed using a material emitting phosphorescence (phosphorescent material) has higher emission efficiency
Implementation Method 3
research and development have been extensively conducted on light-emitting elements utilizing electroluminescence (EL). Such a light-emitting element has a basic structure in which a layer containing a light-emitting material (an EL layer) is interposed between a pair of electrodes. By application of a voltage between the electrodes of this element, light emission from the light-emitting material can be obtained
Implementation Method 4
application of a voltage between the pair of electrodes causes injection of electrons from the cathode and holes from the anode into the EL layer having a light-emitting property, and thus a current flows. By recombination of the injected electrons and holes, the light-emitting organic material is brought into an excited state to provide light emission
Data Source
AI summary
A light-emitting element with a lower voltage and higher emission efficiency is provided. The light-emitting element includes a first organic compound, a second organic compound, and a guest material. The LUMO level of the first organic compound is lower than the LUMO level of the second organic compound, and a difference between them is larger than 0 eV and smaller than or equal to 0.5 eV. Furthermore, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound. The guest material has a function of converting triplet excitation energy into light emission. The first organic compound and the second organic compound form an exciplex.