Smoothing Layer in Photoelectric Conversion Devices
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Solution Overview
Problem
Conventional photoelectric conversion devices face issues with light use efficiency and false color generation due to the limitations of color filters and wavelength dependency in solid-state imaging devices, leading to pixel failure and deterioration of device characteristics.
Innovation Solution
A photoelectric conversion device with a smoothing layer between the electrodes and a photoelectric conversion layer, composed of organic materials, is introduced to reduce surface roughness and prevent short circuits, enhancing light transmission and uniform electric field application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a transparent conductive oxide electrode is formed by sputtering method, then the electrode can be formed with good processing suitability and smoothness, but sputtered particles enter into the depressed areas of the photoelectric conversion layer surface, causing device short circuit and roughness increase
Solution Approach 1:
The patent applies preliminary action by forming a flattening layer between the photoelectric conversion layer and the transparent conductive oxide electrode before electrode formation. This flattening layer pre-compensates for surface irregularities, preventing sputtered particles from entering depressed areas during subsequent sputtering process, thereby eliminating short circuit risks while maintaining processing suitability.
Solution Approach 2:
The flattening layer serves as an intermediary between the photoelectric conversion layer and the transparent conductive oxide electrode. It mediates the interaction by providing a smooth intermediate surface that prevents direct contact between sputtered particles and depressed areas of the photoelectric conversion layer, thus preventing short circuits while allowing the sputtering process to proceed.
2Ease of manufacture
If the photoelectric conversion layer is made with large roughness polycrystalline material, then the device can be manufactured with certain ease, but the surface roughness causes non-uniform electric field distribution and increases leak current
Solution Approach 1:
The flattening layer is formed in advance to compensate for the inherent roughness of polycrystalline photoelectric conversion layers. This preliminary action creates a smooth surface for subsequent electrode formation without requiring changes to the photoelectric conversion layer manufacturing process, thus maintaining manufacturing ease while achieving surface precision.
Solution Approach 2:
The flattening layer provides local quality improvement by specifically addressing the surface roughness issue at the electrode interface while leaving the bulk properties of the polycrystalline photoelectric conversion layer unchanged. This allows the device to maintain the manufacturing advantages of polycrystalline materials while achieving the surface smoothness required for uniform electric field distribution.
3Measurement precision
If color filters are used for color separation, then color detection can be achieved, but light not transmitted through the color filter is lost, reducing light use efficiency
Solution Approach 1:
The patent transitions from planar color filter-based color separation to three-dimensional stacked photodiode structure for color separation. By utilizing the depth dimension within the semiconductor substrate, different wavelengths are detected at different depths, enabling color separation without blocking other wavelengths, thus improving light use efficiency while maintaining color detection accuracy.
Solution Approach 2:
The patent employs a nested structure where multiple photodiodes with different spectral responses are stacked within the semiconductor substrate. Each photodiode is nested at a different depth, allowing simultaneous detection of multiple wavelengths without mutual interference, thereby eliminating the light loss problem associated with planar color filters.
4Productivity
If the pixel size is reduced for high integration, then the number of pixels increases, but the PD size becomes comparable to visible light wavelength, making light guidance into PD difficult
Solution Approach 1:
The patent uses a nested stacked photodiode structure where multiple photodiodes are arranged vertically within the semiconductor substrate. This three-dimensional nesting allows each photodiode to capture light efficiently at its specific depth while maintaining high pixel density through vertical stacking, thereby resolving the conflict between integration density and light capture efficiency.
Solution Approach 2:
The patent moves from two-dimensional planar pixel arrangement to three-dimensional stacked photodiode configuration. By utilizing the vertical dimension, the system achieves high integration density without reducing the effective light capture area of individual photodiodes, as each stacked photodiode can be optimized for its specific wavelength range at its depth position.
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 solution improves light use efficiency, reduces pixel failure, and maintains device characteristics by preventing short circuits and plasma damage, allowing for effective color separation and stable operation.
Implementation Method 1
a photoelectric conversion layer which is made of an organic material stacked on the first electrode... capable of absorbing incident light having a specified wavelength and generating charges (electrons and holes) corresponding to the quantity of absorbed light
Implementation Method 2
a smoothing layer for reducing roughness of a surface of the photoelectric conversion layer is provided between the first electrode or the second electrode and the photoelectric conversion layer
Implementation Method 3
since such a transparent conductive oxide is in general formed by a sputtering method
Implementation Method 4
since the second electrode is formed by a sputtering method, the photoelectric conversion layer is liable to be damaged due to plasma at the time of sputtering
Data Source
AI summary
A photoelectric conversion device comprising a photoelectric conversion part including a first electrode, a second electrode opposing to the first electrode and a photoelectric conversion layer provided between the first electrode and the second electrode, wherein a smoothing layer for reducing roughness of a surface of the photoelectric conversion layer is provided between the first electrode or the second electrode and the photoelectric conversion layer.