Organic Electroluminescent Element Host Compound Reorganization Energy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current organic electroluminescent elements, particularly those emitting blue light, face challenges in achieving high efficiency due to the generation ratio of singlet to triplet excited species and the requirement for host compounds with specific properties to enhance phosphorescence-based light emission.
Innovation Solution
An organic electroluminescent element is developed with a light emission layer containing a host compound and a phosphorescent compound, where the host compound has a reorganization energy of 0 to 0.50 eV and a phosphorescence wavelength between 300 to 460 nm, and the phosphorescent compound is a metal complex from group VIII, such as an iridium complex, to improve luminance and lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If phosphorescent compound is used as dopant to improve light emission efficiency, then internal quantum efficiency can reach up to 100%, but external quantum efficiency remains limited around 6% due to insufficient host compound properties
Solution Approach 1:
The patent changes the key parameter of host compound selection from conventional criteria (triplet energy level, hole mobility) to reorganization energy (0 to 0.50 eV). This parameter change enables efficient electron injection and transport while maintaining high internal quantum efficiency, resolving the contradiction between theoretical efficiency and practical performance.
Solution Approach 2:
The patent creates a composite light emission layer combining specific host compounds (with reorganization energy 0 to 0.50 eV) and phosphorescent dopants (group VIII metal complexes). This composite structure achieves synergistic effects where the host provides efficient electron transport and the dopant provides phosphorescence emission, improving external quantum efficiency beyond conventional 6% limitation.
2Device complexity
If conventional host compounds (e.g., CBP) are used with phosphorescent dopant, then element structure is simpler, but luminance and lifetime are insufficient for practical use
Solution Approach 1:
The patent introduces reorganization energy as a new selection criterion for host compounds, specifying a range of 0 to 0.50 eV. This parameter change identifies compounds that provide both structural simplicity and enhanced reliability, achieving long element lifetime through efficient electron transport and reduced degradation.
3Illumination intensity
If blue light phosphorescent element is developed, then viewing angle and visuality are improved, but light emission efficiency is insufficient due to triplet energy level requirements
Solution Approach 1:
The patent changes the selection parameter from triplet energy level matching to reorganization energy (0 to 0.50 eV). This enables blue light emission with high efficiency by focusing on electron transport capability rather than energy level alignment, resolving the contradiction between visual quality and energy 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
The solution results in an organic electroluminescent element with enhanced luminance and extended lifetime, achieving higher external quantum efficiency and improved light emission efficiency comparable to cold cathode tubes.
Implementation Method 1
An organic electroluminescent element comprises a light emission layer containing a host compound and a phosphorescent compound
Implementation Method 2
An organic electroluminescent element has a structure in which a light emission layer containing a light emission compound is arranged between a cathode and an anode, and an electron and a hole were injected into the light emission layer and recombined to form an exciton
Data Source
AI summary
Disclosed is an organic electroluminescent element comprising a light emission layer containing a host compound and a phosphorescent compound, the host compound having reorganization energy of from more than 0 to 0.50 eV, wherein the reorganization energy is energy in the process in which the host compound changes to the anion radical, and calculated employing Gaussian 98.