Organic Diode Short Protection via Inorganic Semiconductor Layer
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Solution Overview
Problem
Electro-optically active organic diodes face reliability issues due to shorts between cathode and anode electrodes, primarily caused by high field strengths at defects in the cathode, leading to organic material degradation and increased risk of shorts.
Innovation Solution
An electro-optically active organic diode structure incorporating a cover layer of inert material over the cathode and a short protection layer of inorganic semiconductor material, such as BaSe or binary oxides, to mitigate high field strengths and prevent direct contact between the cathode and organic layers, enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a reactive cathode material with low work function is used to improve electron injection efficiency, then the efficiency is improved, but the reliability deteriorates due to reactivity and short formation
Solution Approach 1:
An inorganic semiconductor layer is introduced as an intermediary between the reactive cathode material and the organic electro-optically active layer. This intermediate layer has moderate electron affinity that allows it to receive electrons from the cathode while protecting the organic layer from direct contact with reactive cathode materials, thus maintaining electron injection efficiency while improving reliability
Solution Approach 2:
The cathode structure is designed as a composite system combining a reactive low work function material with an inorganic semiconductor layer. This composite structure leverages the electron injection capability of the reactive material while the inorganic semiconductor provides stability and protection, achieving both high efficiency and reliability
2Duration of action of stationary object
If the operational lifetime is increased to improve device performance, then the lifetime is improved, but the reliability worsens due to short formation between electrodes
Solution Approach 1:
The inorganic semiconductor layer is deposited in advance during the fabrication process, before the device is put into operation. This preliminary protective action prevents direct contact between the cathode and organic layer throughout the device's operational lifetime, preventing short formation while allowing the device to operate for extended periods
Solution Approach 2:
The inorganic semiconductor layer acts as a cushioning barrier that is in place before any potential damage can occur. It absorbs and distributes mechanical and thermal stress that would otherwise directly affect the organic layer, preventing degradation and short formation during extended operation
3Length of moving object
If a thin organic layer is used to reduce device thickness, then the device becomes thinner, but the reliability deteriorates due to increased risk of shorts
Solution Approach 1:
The inorganic semiconductor layer serves as an intermediary that enables the use of thinner organic layers by providing the primary protective barrier against shorts. Since the inorganic material is inherently more stable and less prone to degradation, it compensates for the reduced thickness of the organic layer, maintaining reliability while allowing overall device thinning
4Ease of manufacture
If organic materials are used to enable flexibility and transparency, then ease of manufacture and device properties are improved, but reliability deteriorates due to sensitivity to temperature and pressure
Solution Approach 1:
The device structure is designed as a composite where organic materials provide flexibility and transparency while the inorganic semiconductor layer provides thermal and pressure stability. This composite approach allows the device to maintain the advantageous properties of organic materials while compensating for their weaknesses through the inorganic protective layer
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 the risk of shorts and improves the operational lifetime of electro-optically active organic diodes by using inorganic materials that are less sensitive to temperature and pressure, providing better protection against heat and electrical stress.
Implementation Method 1
one large contributor to unreliable conventional electro-optically active organic diodes, and especially such of large areas, seems to be shorts that occur between cathode and anode electrodes, and the extent of damage such shorts have on the organic material arranged in between. It further seems like one factor contributing to these shorts is the occurrence of high field strengths in the cathode owing to unintentional physical defects in the cathode
Implementation Method 2
said cover layer is formed of a substantially inert material with respect to a cathode layer material in contact with said cover layer
Implementation Method 3
The inorganic semiconductor material is comprising BaSe, or a binary oxide of an alkali earth metal or lanthanide... providing better protection against heat and electrical stress
Data Source
Figure 1~2b
Figure 3
AI summary
An electro-optically active organic diode, for example an organic light emitting diode (OLED), comprises an anode electrode (102), a cathode electrode (122) and an electro-optically active organic layer (110) arranged in-between. A cover layer (124) is arranged in contact with a surface of the cathode layer (122) so that the cathode layer (122) is positioned between the organic layer (110) and the cover layer (124), which is formed of a substantially inert material with respect to a cathode layer (122) material in contact with said cover layer (124). The inert material is deposited on said surface of the cathode layer (122) so that the complete surface is covered and surface defects eliminated. A short protection layer (120) is further arranged between said cathode electrode (122) and said electro-optically active organic layer (110), and adjacent to said cathode electrode (122), and is formed of an inorganic semiconductor material. The cover layer (124) and the short protection layer (120) together reduce the risk of shorts to occur between the cathode (122) and the anode (102) and thus increase reliability of the electro-optically active organic diode.