Image Sensor with Stacked Organic Layer and Metal Electrode
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Solution Overview
Problem
Conventional image sensors with silicon photodiodes have limited sensitivity due to small pixel sizes and absorption areas, and existing color filters result in significant light loss before reaching the photodiode, hindering the reduction of pixel size and light efficiency.
Innovation Solution
An image sensor design incorporating a semiconductor substrate with a light-transmitting electrode and a metal layer, along with an organic photoelectric conversion layer that absorbs light in specific wavelength regions, eliminating the need for a separate organic color filter and allowing for reduced pixel size while enhancing wavelength selectivity and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a silicon photodiode is used in small pixels to achieve high resolution, then the pixel size can be reduced, but the absorption area becomes too small resulting in deteriorated sensitivity
Solution Approach 1:
The patent introduces a vertical stacking architecture where multiple photodiodes sensing different wavelength regions are arranged in the depth direction rather than horizontally. This dimensional change allows each pixel to maintain small horizontal footprint for high resolution while increasing the effective light absorption volume vertically, thereby improving sensitivity without sacrificing resolution.
Solution Approach 2:
The patent employs an organic photoelectric conversion layer with specific wavelength selectivity properties combined with silicon photodiodes. This composite structure enables the organic layer to pre-filter and direct specific wavelength regions to appropriate photodiodes, enhancing the effective absorption area for each wavelength region and improving overall sensitivity while maintaining small pixel size.
2Measurement precision
If a conventional color filter is used to achieve wavelength selectivity, then color separation is achieved, but light loss increases before light reaches the photodiode
Solution Approach 1:
The patent removes the conventional color filter layer from the optical path and replaces it with wavelength-selective photodiodes positioned at different depths. This extraction eliminates the light-absorbing color filter that caused energy loss, while the photodiodes themselves perform the wavelength selection function through their inherent spectral response characteristics.
Solution Approach 2:
The patent introduces an organic photoelectric conversion layer as an intermediary between the incident light and the silicon photodiodes. This intermediary layer provides wavelength selectivity through its optical absorption properties, directing different wavelength regions to appropriate photodiodes without the significant light loss associated with conventional color filters.
3Measurement precision
If a color filter is disposed on each pixel to achieve wavelength selectivity, then color separation is improved, but the pixel size cannot be reduced further due to manufacturing process limitations
Solution Approach 1:
The patent resolves the pixel size limitation by moving the wavelength selection function from the horizontal plane (color filter on pixel surface) to the vertical dimension (stacked photodiodes at different depths). This allows pixels to maintain minimal horizontal footprint while accommodating multiple wavelength-selective sensing elements vertically, enabling further pixel size reduction without sacrificing color separation capability.
Solution Approach 2:
The stacked photodiode structure serves multiple functions within a single vertical column: each photodiode layer senses a different wavelength region, and the stack collectively provides full-color imaging capability. This multi-functional integration eliminates the need for separate color filter structures, allowing pixel dimensions to be reduced to the limit of photodiode fabrication while maintaining complete wavelength selectivity.
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 design improves light efficiency and sensitivity by selectively transmitting and reflecting light in different wavelength regions, achieving high absorption rates without the need for a separate color filter, thus enabling smaller pixel sizes and improved color separation characteristics.
Implementation Method 1
an organic photoelectric conversion layer disposed on the first electrode wherein the organic photoelectric conversion layer absorbs light in a different wavelength region from a wavelength region sensed by the photo-sensing device
Implementation Method 2
The metal layer may be a semi-transmitting layer selectively transmitting light
Data Source
AI summary
An image sensor includes a semiconductor substrate integrated with at least a photo-sensing device, a plurality of first electrodes disposed on the semiconductor substrate, an organic photoelectric conversion layer disposed on the first electrodes, and a second electrode disposed on the organic photoelectric conversion layer. The first electrodes include a light-transmitting electrode and a metal layer interposed between the semiconductor substrate and the light-transmitting electrode. The organic photoelectric conversion layer disposed on the first electrodes and the photo-sensing device absorb and/or sense light in different wavelength regions from each other. An electronic device including the image sensor is also provided.