OLED Hole Injection Layer Layout for Lower Voltage Emission
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Solution Overview
Problem
Existing organic light-emitting devices face challenges in achieving low operational voltage while maintaining high efficiency, as the balance of hole and electron injection is not optimized, leading to suboptimal performance.
Innovation Solution
Incorporating a second hole injection layer with halogenated fullerenes or partially/fully halogenated metal complexes between the first hole transport layer and the light-emitting layer, along with additional hole transport matrix compounds, to enhance the electronic properties and efficiency of the device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional hole injection layers with nitrile functional groups are used, then hole injection is achieved, but operational voltage remains high and efficiency is suboptimal
Solution Approach 1:
The hole injection function is divided into two separate layers: a first hole injection layer adjacent to the anode and a second hole injection layer adjacent to the emission layer. This segmentation allows each layer to be optimized for its specific function, with the second layer using halogenated fullerene compounds to improve hole injection efficiency and reduce operational voltage without compromising overall device performance
Solution Approach 2:
The second hole injection layer acts as an intermediary between the first hole injection layer and the emission layer. By introducing halogenated fullerene compounds in this intermediate position, the patent facilitates more efficient charge transfer and balance between holes and electrons, thereby reducing energy loss and improving overall device efficiency
2Reliability
If a single hole injection layer is used, then device structure is simple, but hole and electron injection balance is not optimized
Solution Approach 1:
The hole injection function is divided into two separate layers: a first hole injection layer adjacent to the anode and a second hole injection layer adjacent to the emission layer. This segmentation allows each layer to be optimized for its specific function, with the second layer using halogenated fullerene compounds to improve hole injection efficiency and reduce operational voltage without compromising overall device performance
Solution Approach 2:
Different regions of the device are assigned different material properties: the first hole injection layer uses conventional nitrile-based compounds optimized for anode interface, while the second hole injection layer uses halogenated fullerene compounds optimized for emission layer interface. This local optimization of material properties achieves superior charge balance without requiring complex overall architecture
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 results in lower operational voltage and higher efficiency for the organic light-emitting device, providing broader design freedom and improved performance characteristics.
Implementation Method 1
holes injected from the anode electrode move to the EML, via the HTL, and electrons injected from the cathode electrode move to the EML, via the ETL
Implementation Method 2
The holes and electrons recombine in the EML to generate excitons. When the excitons drop from an excited state to a ground state, light is emitted
Data Source
AI summary
The present Invention relates to an organic light emitting device comprising: (i) an anode; (ii) a cathode; (iii) at least one light emitting layer arranged between the anode and the cathode; (iv) optionally a first hole injection layer comprising a first hole injection compound, the first hole injection layer being arranged between the anode and the light emitting layer and the hole injection layer being adjacent to the anode; (v) a first hole transport layer comprising a first hole transport matrix compound wherein the first hole transport layer is arranged a) between the first hole injection layer and the light emitting layer and adjacent to the first hole injection layer; or b) between the anode and the light emitting layer and adjacent to the anode; (vi) a second hole injection layer arranged between the first hole transport layer and the light emitting layer, wherein the second hole injection layer is adjacent to the first hole transport layer and wherein the second hole injection layer comprises a second hole injection compound; wherein the second hole injection compound is a halo-genated fullerene, a partially or fully halogenated metal complex or a mixture thereof.