Organic EL Light-Emitting Layer Carrier Density Optimization
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Solution Overview
Problem
Conventional organic electroluminescence (EL) elements suffer from low light emittance efficiency due to an imbalance in the injection of electrons and holes into the light-emitting layer, which affects their performance and efficiency.
Innovation Solution
An organic EL element configuration that includes an anode, a first functional layer with hole injection or transport properties, a light-emitting layer doped with an electron donor material, a second functional layer with electron injection or transport properties, and a cathode, where the carrier density of the light-emitting layer is optimized between 10^12/cm^3 to 10^19/cm^3 to balance electron and hole injection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional organic EL elements are used with standard doping levels, then the structure is simple, but light emittance efficiency is low due to carrier imbalance
Solution Approach 1:
The patent applies parameter changes by optimizing the doping concentration of electron donor materials in the light-emitting layer to achieve carrier density between 10^12/cm³ to 10^19/cm³. This parameter optimization balances electron and hole injection, resolving the contradiction between structural simplicity and light emittance efficiency.
2Productivity
If high carrier density is achieved through heavy doping, then light emittance efficiency improves, but drive voltage increases
Solution Approach 1:
The patent uses parameter changes by precisely controlling carrier density within the optimal range of 10^12/cm³ to 10^19/cm³ through controlled doping. This prevents excessive doping that would increase drive voltage while still achieving sufficient carrier balance for high light emittance efficiency.
Solution Approach 2:
The patent introduces electron donor materials as intermediary substances that mediate between the electrodes and the light-emitting layer. These intermediaries facilitate balanced carrier injection without requiring high drive voltages, resolving the contradiction between efficiency and energy consumption.
3Productivity
If electron donor material is added to the light-emitting layer, then carrier balance improves, but manufacturing complexity increases
Solution Approach 1:
The patent applies parameter changes by optimizing the doping concentration of electron donor materials to achieve carrier density between 10^12/cm³ to 10^19/cm³. This parameter optimization balances electron and hole injection, resolving the contradiction between structural simplicity and light emittance efficiency.
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 enhances light emittance efficiency while allowing the organic EL element to be driven at a low voltage, optimizing carrier movement and improving exciton generation efficiency.
Implementation Method 1
Organic EL elements have at least a light-emitting layer between a pair of electrodes... When driven, a voltage is applied between the pair of electrodes, and light is emitted as the result of recombination of holes injected to the light-emitting layer from the anode and electrons injected to the light-emitting layer from the cathode
Data Source
AI summary
An organic electroluminescence (EL) element including: an anode; a first functional layer above the anode, the first functional layer having at least one of a hole injection property and a hole transport property; a light-emitting layer above the first functional layer, the light-emitting layer including an organic light-emitting material doped with an electron donor material; a second functional layer above the light-emitting layer, the second functional layer having at least one of an electron injection property and an electron transport property; and a cathode disposed above the second functional layer, wherein carrier density of the light-emitting layer is from 1012/cm3 to 1019/cm3.