Organic Image Sensor Carrier Blocking Layer Design
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Solution Overview
Problem
In organic image sensors, increasing the thickness of the first carrier blocking layer to reduce capacity leads to a significant reduction in external quantum efficiency and an increase in dark current, making existing materials unsuitable for practical applications.
Innovation Solution
The use of a carrier blocking layer formed from specific materials with structural formulas (1), (2), or (3), having a thickness of 5×10−9 to 1.5×10−7 m, which minimizes light absorption and maintains high external quantum efficiency while suppressing dark current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the thickness of the first carrier blocking layer is increased to reduce electric capacity, then the electric capacity is reduced, but the external quantum efficiency is significantly reduced and dark current increases
Solution Approach 1:
The patent applies parameter changes by selecting specific organic compound structures (formulas 1-3) with optimized molecular weights and light absorption characteristics, and by precisely controlling the thickness parameter within 5-150 nm range, achieving both low capacity and high quantum efficiency
Solution Approach 2:
The patent uses composite material approach by combining the carrier blocking layer material with specific organic photoelectric conversion layer materials, creating a multi-layer structure where each layer is optimized for its specific function while working together to achieve overall performance
2Quantity of substance
If the thickness of the first carrier blocking layer is increased to reduce capacity, then the electric capacity is reduced, but the dark current increases
Solution Approach 1:
The patent changes the material parameters by selecting organic compounds with specific molecular structures (formulas 1-3) that have appropriate HOMO/LUMO energy levels and low light absorption in the visible range, combined with precise thickness control, to simultaneously reduce capacity and suppress dark current
3Measurement precision
If a conventional color filter is used, then the spectral sensitivity is improved, but approximately 40% of transmitted light is lost due to absorption
Solution Approach 1:
The patent extracts the color filtering function from the traditional separate color filter layer and integrates it into the organic photoelectric conversion layer itself, which inherently exhibits wavelength-dependent photoelectric conversion efficiency, thereby eliminating the need for a dedicated color filter that would absorb and waste light
Solution Approach 2:
The patent merges the color filtering function with the photoelectric conversion function into a single integrated layer, where the organic photoelectric conversion layer simultaneously performs both wavelength selection and charge generation, eliminating the separate color filter component
4Area of moving object
If the pixel size is miniaturized to improve recording density, then the recording density is improved, but light leakage from adjacent pixels increases and incident angle is restricted
Solution Approach 1:
The patent employs thin film technology by using organic photoelectric conversion layers with thickness of 5-200 nm, which are sufficiently thin to allow light to reach the photoelectric conversion layer without being blocked by thick inactive layers, thereby reducing light leakage and relaxing incident angle restrictions in miniaturized pixels
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 achieves both good external quantum efficiency and spectral characteristics, reduces electric capacity, and improves dark current vs. voltage characteristics, resulting in high-quality imaging with reduced residual images.
Implementation Method 1
photoelectric conversion by organic semiconductor materials
Implementation Method 2
carrier blocking layer
Data Source
AI summary
An image sensor includes at least a first electrode, a second electrode, an organic photoelectric conversion layer, and a carrier blocking layer. The carrier blocking layer is formed of a material having the following structural formula (1), and has a thickness of from 5×10−9 to 1.5×10−7 m: