Charge Generating Layer Doping for Leakage Current Reduction
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Solution Overview
Problem
Light emitting devices face challenges with leakage current, which affects display quality and efficiency, particularly due to unintended pixel activation from lateral current leakage.
Innovation Solution
Incorporating multiple light emitting units with overlapping electrodes and strategically positioned charge generating layers, including n-type layers doped with alkali metals like lithium and lanthanum, to manage charge balance and reduce leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional charge generating layers are used in light emitting devices, then device structure is simple, but leakage current increases causing poor display quality
Solution Approach 1:
The charge generating layer is divided into multiple distinct layers (first charge generating layer, second charge generating layer, third charge generating layer) with different dopant compositions. Each layer serves specific functions: the first layer with alkali metal dopant generates positive charges, the second layer with lanthanum dopant generates negative charges, and the third layer balances charges. This segmentation allows precise control of charge distribution to reduce leakage current while maintaining manageable structural complexity.
Solution Approach 2:
Different regions of the charge generating layer structure are assigned different dopant types and concentrations tailored to local requirements. The first charge generating layer uses alkali metal dopants (0.1-3 vol%) optimized for positive charge generation near the anode, while the second layer uses lanthanum dopants (1-10 vol%) for negative charge generation. This local optimization of material properties enables effective leakage current suppression throughout the device.
2Reliability
If multiple dopants are used in charge generating layers, then leakage current is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The invention specifies precise dopant concentration ranges to optimize performance while accounting for manufacturing variability. Alkali metal dopants are controlled at 0.1-3 vol% and lanthanum dopants at 1-10 vol%. These parameter windows are engineered to provide robust leakage current reduction even with typical manufacturing tolerances, balancing performance optimization with manufacturing feasibility.
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 effectively reduces leakage currents, enhancing display quality by preventing parasitic lighting and improving color linearity and purity, while maintaining efficient light emission characteristics.
Implementation Method 1
at least one of a plurality of n-type charge generating layers includes a dopant including an alkali metal, and at least one of a plurality of n-type charge generating layers includes a dopant including a lanthanum metal
Implementation Method 2
the charge generating layer includes: an n-type charge generating layer and a p-type charge generating layer
Data Source
AI summary
A light emitting device includes: a first electrode; a second electrode overlapping the first electrode; m light emitting units between the first electrode and the second electrode; and m-1 charge generating layers between adjacent light emitting units, wherein the charge generating layer includes: an n-type charge generating layer and a p-type charge generating layer; at least one of a plurality of n-type charge generating layers includes a dopant including an alkali metal, and at least one of a plurality of n-type charge generating layers includes a dopant including a lanthanum metal; contents of the alkali metal and the lanthanum metal doped in the n-type charge generating layer are different from each other; and the m is a natural number of greater than or equal to 3.