OLED Substrate Auxiliary Cathode for Brightness Uniformity
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Solution Overview
Problem
Top-emitting OLEDs face challenges in balancing light transmittance and electrical conductivity, leading to non-uniform brightness and color shift with viewing angle due to the cathode's resistance and thickness requirements.
Innovation Solution
The method involves forming a relatively thick auxiliary cathode between two pixel defining layers and a thin cathode in the pixel region, connected to the auxiliary cathode, to improve light transmittance and electrical conductivity, ensuring uniform voltage distribution and reducing color shift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cathode is made thicker to improve electrical conductivity, then electrical conductivity is improved, but light transmittance deteriorates
Solution Approach 1:
The cathode system is divided into two parts: a thick auxiliary cathode (first cathode) for electrical conductivity and a thin cathode (second cathode) for light transmittance. The auxiliary cathode has a thickness of 50-200 nm while the main cathode has a thickness of 5-20 nm, allowing each layer to optimize its function without compromising the other.
Solution Approach 2:
Different regions of the cathode structure have different thicknesses optimized for different functions. The auxiliary cathode region provides high electrical conductivity where light emission is not needed, while the main cathode region provides high light transmittance where light emission occurs. This local differentiation resolves the contradiction between conductivity and transmittance.
2Illumination intensity
If the cathode is made thinner to improve light transmittance, then light transmittance is improved, but electrical conductivity deteriorates leading to non-uniform brightness
Solution Approach 1:
The cathode is segmented into an auxiliary cathode layer and a main cathode layer. The auxiliary cathode (first cathode) with thickness of 50-200 nm provides the electrical conductivity pathway, while the thin main cathode (second cathode) with thickness of 5-20 nm provides light transmittance. This segmentation allows the thin cathode to maintain high transmittance while the auxiliary cathode ensures sufficient conductivity.
3Reliability
If a single thick cathode is used to ensure electrical conductivity, then electrical conductivity is improved, but brightness uniformity deteriorates due to voltage distribution issues
Solution Approach 1:
The cathode structure is segmented into an auxiliary cathode and a main cathode. The auxiliary cathode serves as an electrical conduction pathway that distributes voltage uniformly across the pixel electrode, while the thin main cathode allows uniform light emission. This segmentation resolves the voltage distribution issue that causes brightness non-uniformity in single-thick-cathode designs.
Solution Approach 2:
The auxiliary cathode acts as an intermediary layer between the electrode and the thin main cathode. It provides the electrical conduction function that would otherwise require a thick main cathode, thereby enabling the main cathode to remain thin and ensure both uniform voltage distribution and high light transmittance.
4Use of energy by moving object
If the cathode is made thinner to reduce power consumption, then power consumption is reduced, but electrical conductivity deteriorates
Solution Approach 1:
The cathode is segmented into an auxiliary cathode layer and a main cathode layer. The auxiliary cathode provides the necessary electrical conductivity pathway, allowing the main cathode to be made thin (5-20 nm) to reduce power consumption while maintaining sufficient conductivity through the auxiliary layer.
Data Source
AI summary
An organic light emitting diode substrate, a method for manufacturing an organic light emitting diode substrate, and a display panel. The organic light emitting diode substrate includes: a base substrate; a pixel defining layer on the base substrate; and an anode, an organic light emitting diode functional layer and a cathode in a pixel region. The pixel defining layer includes a first pixel defining layer, an auxiliary cathode and a second pixel defining layer sequentially stacked, the auxiliary cathode being connected to the cathode.