Heterocyclic Host Material for OLED Voltage and Lifetime
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Solution Overview
Problem
Organic light emitting display devices face challenges in reducing operating voltage and improving efficiency and lifetime due to materials with high triplet energy causing efficiency decreases and voltage rises, while materials with low thermal and electric stability shorten device lifespan.
Innovation Solution
A heterocyclic compound with a rigid structure and high triplet energy, incorporating spirobisfluorene and heteroaryl groups, is used as a host in the light emitting layer to facilitate efficient energy transfer and enhance thermal and electric stability, reducing operating voltage and increasing device lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If materials with high triplet energy are used in the light emitting layer, then energy transfer efficiency is improved, but operating voltage increases and device efficiency decreases
Solution Approach 1:
The patent modifies the chemical structure of host materials by introducing specific heterocyclic groups (triazole, oxadiazole, tetrazole) and spirobisfluorene core structures. These structural changes alter the energy level parameters of the material, achieving high triplet energy (2.5-3.0 eV) while simultaneously optimizing HOMO/LUMO levels to reduce operating voltage and improve charge transport efficiency.
Solution Approach 2:
The patent employs composite molecular structures combining spirobisfluorene core with heterocyclic substituents (triazole, oxadiazole, tetrazole groups). This composite approach creates materials that simultaneously achieve high triplet energy for efficient energy transfer and appropriate charge transport properties for low operating voltage, resolving the contradiction between energy efficiency and power consumption.
2Use of energy by moving object
If materials with high triplet energy are used in the light emitting layer, then energy transfer efficiency is improved, but device efficiency decreases
Solution Approach 1:
The patent optimizes the triplet energy parameter to a specific range (2.5-3.0 eV) that matches the dopant materials, maximizing energy transfer efficiency. Simultaneously, the molecular structure is designed to minimize non-radiative decay pathways, ensuring that absorbed energy is converted to light emission rather than heat loss, thereby improving overall device efficiency.
3Ease of manufacture
If materials with low thermal stability are used, then manufacturing cost is reduced, but device lifetime decreases
Solution Approach 1:
The patent introduces rigid spirobisfluorene core structures and stable heterocyclic groups (triazole, oxadiazole, tetrazole) that inherently provide high thermal stability. These structural parameters ensure the material maintains its properties at elevated temperatures during device operation, preventing degradation and extending device lifetime while remaining compatible with standard manufacturing processes.
4Ease of manufacture
If materials with low electric stability are used, then manufacturing cost is reduced, but device lifetime decreases
Solution Approach 1:
The patent designs composite molecular structures combining spirobisfluorene with electrically stable heterocyclic groups. This composite approach creates materials with superior electric stability that resist degradation under electrical stress, ensuring long device lifetime. The molecular structure is optimized to facilitate charge transport while maintaining stability, achieving both performance and durability without requiring complex manufacturing processes.
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 heterocyclic compound achieves a 13-21% decrease in operating voltage, a 6-21% increase in external quantum efficiency, and a 390-498% increase in lifetime by ensuring energy is consumed for light emission rather than thermal dissipation, while maintaining high triplet energy for efficient energy transfer.
Implementation Method 1
For efficient energy transfer from the host to the dopant, the triplet energy of the host must be greater than the triplet energy of the dopant
Implementation Method 2
Since the excitons transferred to the singlets of the dopant are transferred to the triplets of the dopant by intersystem crossing
Implementation Method 3
excitons are formed by the recombination of electrons and holes injected from the two electrodes
Data Source
AI summary
An organic light emitting display device is disclosed. The organic light emitting display device comprises an anode, an organic layer over the anode, and a cathode over the organic layer. The organic layer may include a heterocyclic compound. Alternatively, the organic layer may include a spirobisfluorene compound with hole transfer properties and a material with electron transfer properties.