Buffer-Assisted Charge Generation Layer for Tandem OLEDs
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Solution Overview
Problem
Conventional tandem Organic Light Emitting Diodes (OLEDs) face inefficiencies in charge injection due to misaligned energy levels in the charge generation layer (CGL), leading to reduced brightness and current efficiency.
Innovation Solution
A buffer assisted charge generation layer is introduced, comprising a junction of p-type and n-type doped semiconductor layers surrounded by hole and electron buffer layers, enhancing charge injection into adjacent emissive layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional charge generation layer with p-type and n-type semiconductor junction is used, then charge generation occurs, but energy level misalignment with adjacent organic light emissive layers leads to inefficient charge injection
Solution Approach 1:
The patent introduces buffer layers as intermediary components between the charge generation layer and the adjacent organic light emissive layers. These buffer layers serve as energy level mediators that facilitate efficient charge injection by bridging the energy gap between the semiconductor junction and the organic emissive layers, thereby resolving the energy level misalignment problem without requiring changes to the core charge generation mechanism
Solution Approach 2:
The charge generation layer is constructed as a composite structure combining p-type and n-type doped semiconductor layers in a junction configuration. This composite material approach enables simultaneous achievement of charge generation functionality and improved energy level alignment when combined with buffer layers, addressing both the charge generation requirement and the injection efficiency problem
2Productivity
If tandem OLED structure with multiple EL units is used, then current efficiency and brightness are improved, but charge injection efficiency is reduced due to energy level misalignment in CGL
Solution Approach 1:
The buffer layers act as intermediary components that enable the tandem OLED structure to achieve both high current efficiency and high charge injection efficiency. By placing buffer layers at the interfaces between the charge generation layer and each emissive layer, the patent ensures that charges generated in the CGL can be efficiently injected into multiple EL units, maintaining the productivity benefits of tandem structure while eliminating the injection efficiency problem
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 significantly improves the external quantum efficiency of tandem OLEDs, doubling the brightness at the same current density compared to single OLED units, demonstrating efficient charge injection and enhanced performance.
Implementation Method 1
a junction of a p-type doped semiconductor layer and an n-type doped semiconductor layer, where free electrons and holes are generated
Implementation Method 2
these free electrons and holes in the CGL can transport and inject into their adjacent EL units
Data Source
AI summary
A tandem Organic Light Emitting Diode (OLED) apparatus and method of fabricating the same, where the tandem OLED apparatus includes a buffer assisted charge generation layer having a junction of a p-type doped semiconductor layer and an n-type doped semiconductor layer, where a hole buffer layer and an electron buffer layer pair surrounding the junction of the p-type and n-type doped semiconductor layers. The OLED apparatus further includes a first OLED emissive layer and a second OLED emissive layer pair surrounding the buffer assisted charge generation layer, and a cathode and anode layer pair further surrounding the first and second OLED emissive layer pair.