Common Charge Generation Layer for OLED Pixel Crosstalk
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Solution Overview
Problem
Active OLED displays face significant challenges with pixel crosstalk, particularly due to redox p-doping in hole transport layers, which increases electrical conductivity and leads to unwanted light emission from adjacent pixels, affecting overall display performance.
Innovation Solution
A display device with vertically stacked electroluminescent units and a common charge generation layer comprising an organic electron transport compound and a metal dopant for the n-type layer, and an organic hole transport compound with a high concentration of organic p-dopant for the p-type layer, optimizing hole and electron mobility to reduce crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redox p-doping is used in hole transport layers to increase electrical conductivity, then charge injection is improved, but pixel crosstalk increases due to unwanted light emission from adjacent pixels
Solution Approach 1:
The patent divides the charge generation function into separate n-type and p-type charge generation layers, each with specific doping characteristics. The n-type layer uses redox n-doping while the p-type layer uses redox p-doping, allowing independent optimization of electron and hole injection without cross-interference that causes pixel crosstalk
Solution Approach 2:
The patent applies different doping strategies to different regions: the n-type charge generation layer uses redox n-doping with electron transport compounds, while the p-type layer uses redox p-doping with hole transport compounds. This localized differentiation allows each layer to optimize charge injection for its specific carrier type while minimizing unwanted charge leakage to adjacent pixels
2Reliability
If doping substances are added to transport layers to increase equilibrium charge-carrier concentration, then electrical conductivity is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple functions into the charge generation layers: they serve as both charge injection layers and charge transport layers. By integrating the doping function directly into the charge generation layers rather than adding separate doped transport layers, the patent reduces overall device complexity while maintaining high electrical conductivity
Solution Approach 2:
The charge generation layers perform multiple functions simultaneously: they generate charges through doping, transport charges through their inherent transport properties, and provide interfaces for charge injection. This multi-functionality eliminates the need for separate dedicated transport layers, simplifying the overall device structure
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 minimizes crosstalk between pixels while maintaining good overall OLED performance by controlling charge mobility and injection, enhancing the display's operational stability and efficiency.
Implementation Method 1
common n-type charge generation layer comprising an organic electron transport compound and a metal dopant
Implementation Method 2
common p-type charge generation layer comprising an organic hole transport compound and an organic p-dopant
Implementation Method 3
each pixel of the plurality of pixels comprises at least two vertically stacked electroluminescent units and at least one charge generation layer arranged between the at least two vertically stacked electroluminescent units; wherein each electroluminescent unit comprises at least one light-emitting layer
Data Source
AI summary
The present invention relates to a display device comprising a common charge generation layer and method for making the same.