Organic photoelectric conversion element, optical area sensor, imaging device, and imaging apparatus
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Solution Overview
Problem
Existing organic photoelectric conversion elements with a hole blocking layer containing a fullerene derivative face inefficiencies in hole transfer to the hole-collecting electrode, limiting their sensitivity and response speed.
Innovation Solution
Incorporating a second organic compound layer with an ionization potential of 5.1 eV or less and a band gap of 2.5 eV or more between the photoelectric conversion layer and the cathode, allowing efficient hole transfer while preventing electron flow, and using water-resistant compounds like imidazolidene derivatives to enhance stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hole blocking layer containing a fullerene derivative is used, then electron blocking capability is improved, but hole transfer efficiency to the hole-collecting electrode deteriorates
Solution Approach 1:
The hole blocking layer is divided into two distinct layers: a first hole blocking layer containing a fullerene derivative (for electron blocking) and a second hole blocking layer containing an organic compound with specific properties (ionization potential 5.5 eV or more, band gap 2.85 eV or more). This segmentation allows each layer to perform its specialized function without interfering with the other, resolving the contradiction between electron blocking and hole transfer efficiency
Solution Approach 2:
The second hole blocking layer acts as an intermediary between the photoelectric conversion layer and the hole-collecting electrode. It mediates the interaction by providing a pathway for efficient hole transfer while maintaining the electron blocking function of the first layer, thus enabling both electron blocking and hole collection to occur simultaneously without conflict
2Reliability
If the organic compound has high ionization potential (5.5 eV or more) for electron blocking, then electron flow prevention is improved, but hole mobility to the electrode deteriorates
Solution Approach 1:
The hole blocking function is segmented between two layers with different property profiles. The first layer (fullerene derivative) provides electron blocking, while the second layer (high ionization potential compound) provides hole blocking while still allowing hole transfer to the electrode. This segmentation resolves the contradiction by distributing functions across layers rather than requiring a single material to satisfy conflicting requirements
Solution Approach 2:
Different regions of the hole blocking structure are assigned different local qualities: the first layer has high electron affinity for electron blocking, while the second layer has high ionization potential for hole management. This local differentiation allows each region to optimize for its specific function, enabling electron blocking without compromising hole mobility to the electrode
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 enables efficient hole transfer and prevents electron flow, improving the sensitivity and response speed of the organic photoelectric conversion element while maintaining water resistance and reducing noise in imaging devices.
Implementation Method 1
photoelectric conversion portion that converts light into charges
Implementation Method 2
holes can be efficiently transferred from the photoelectric conversion portion to the cathode
Implementation Method 3
electrons are prevented from flowing into the photoelectric conversion portion from the cathode
Data Source
Figure 1~2
AI summary
An organic photoelectric conversion element includes an anode, a cathode, and a photoelectric conversion portion between the anode and the cathode. The photoelectric conversion portion includes a first organic compound layer containing an organic compound. Also, a second organic compound layer is disposed between the cathode and the photoelectric conversion portion. The second organic compound layer contains an organic compound having an ionization potential of 5.1 eV or less and a band gap of 2.5 eV or more.