Organic Photoelectric Conversion Device with Electron Blocking Layer
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Solution Overview
Problem
Conventional photoelectric conversion devices for solid-state imaging suffer from reduced sensitivity and increased dark current due to small pixel size, heat resistance issues, and inadequate charge transportability, particularly when used in imaging devices that require high photoelectric conversion efficiency and heat resistance.
Innovation Solution
A photoelectric conversion device with a specific compound structure, comprising a transparent electrically conductive film, a photoelectric conversion layer containing a fullerene or fullerene derivative, and an electron blocking layer with a compound represented by formula (F-1), which enhances charge transportability and reduces dark current even under high temperature conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pixel size is reduced to increase the number of pixels, then the resolution is improved, but the aperture ratio and light collection efficiency are reduced
Solution Approach 1:
The patent changes the material parameter of the photoelectric conversion layer from conventional inorganic materials to organic materials with specific molecular structures (containing carbazole, triphenylamine, or xylene groups). This material parameter change enables high photoelectric conversion efficiency even in small pixel areas, effectively resolving the contradiction between high resolution and sufficient light collection efficiency.
2Productivity
If a voltage is externally applied to enhance photoelectric conversion efficiency and response speed, then the photoelectric conversion efficiency is improved, but the dark current increases due to charge injection from electrodes
Solution Approach 1:
The patent changes the energy level parameters of the photoelectric conversion layer by selecting organic materials with specific HOMO and LUMO levels. The HOMO level is set higher than the electrode work function (4.5-5.0 eV) and the LUMO level is set lower than the electrode work function, creating energy barriers that prevent charge injection while maintaining efficient photoelectric conversion.
Solution Approach 2:
The patent introduces the organic photoelectric conversion layer as an intermediary between the electrode and the photoelectric conversion process. This intermediate layer with specifically tuned energy levels acts as a buffer that allows efficient exciton dissociation while blocking direct charge injection from the electrode, thus reducing dark current.
3Productivity
If conventional organic photoelectric conversion materials are used, then the photoelectric conversion efficiency is improved, but the heat resistance is insufficient for high temperature processing
Solution Approach 1:
The patent changes the thermal stability parameters of the organic materials by selecting compounds with high glass transition temperatures (Tg > 100°C) and high decomposition temperatures. Specific molecular structures containing carbazole, triphenylamine, or xylene groups are chosen to achieve both high photoelectric conversion efficiency and sufficient heat resistance for high temperature processing.
4Measurement precision
If the pixel size is reduced, then the resolution is improved, but the sensitivity is reduced due to reduced light collection efficiency
Solution Approach 1:
The patent changes the photoelectric conversion parameters of the material by using organic materials with high exciton dissociation efficiency and appropriate energy levels. This enables small pixels to maintain high sensitivity despite reduced light collection area, as the organic photoelectric conversion layer efficiently converts the collected light into electrical signals.
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 device achieves low dark current and improved heat resistance, maintaining high photoelectric conversion efficiency and response speed, even during heat treatment processes, making it suitable for imaging devices.
Implementation Method 1
photoelectric conversion layer containing a fullerene or fullerene derivative
Implementation Method 2
a technique of providing a charge blocking layer to suppress the injection of an electric charge into the photoelectric conversion layer
Data Source
Figure 1A~1B
Figure 2
AI summary
A photoelectric conversion device comprising a transparent electrically conductive film, a photoelectric conversion film and an electrically conductive film in this order, wherein the photoelectric conversion film comprises a photoelectric conversion layer, and an electron blocking layer, wherein the electron blocking layer contains a compound represented by the specific formula.