Photoelectric Conversion Device Spectral Sensitivity Optimization
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Solution Overview
Problem
Conventional solid-state imaging devices face issues with low sensitivity and broad spectral sensitivity due to inefficient light absorption and transfer of charge carriers in photoelectric conversion layers, particularly in organic materials, leading to false colors and optical losses.
Innovation Solution
A photoelectric conversion device is designed with a photoelectric conversion layer that generates charges in the vicinity of the second electrode layer, where the first electrode layer extracts holes and transfers them to a charge storage part in the semiconductor substrate, enhancing photoelectric conversion efficiency and spectral sensitivity by using organic p-type and n-type semiconductors like quinacridone derivatives and optimizing electrode materials like ITO and ZnO2.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If light is made incident from the upper part of the second electrode layer into the photoelectric conversion layer, then the photoelectric conversion efficiency is improved, but the spectral sensitivity broadens and sensitivity is reduced
Solution Approach 1:
The patent applies local quality by creating different functional regions within the photoelectric conversion layer. The first electrode layer is designed to extract holes locally, while the second electrode layer extracts electrons. This local differentiation of charge carrier extraction zones prevents the broadening of spectral sensitivity while maintaining high photoelectric conversion efficiency, as each region is optimized for its specific function.
Solution Approach 2:
The patent introduces an intermediary charge storage part formed in the semiconductor substrate to store holes transferred from the first electrode layer. This intermediary structure mediates between the photoelectric conversion layer and the readout circuit, allowing efficient charge collection while maintaining sharp spectral sensitivity by preventing charge carrier recombination and reducing dark current.
2Measurement precision
If color filters are arranged to transmit only specific wavelengths, then color separation is achieved, but light utilization efficiency is reduced
Solution Approach 1:
The patent extracts the color filter layer from the optical path by implementing color separation through the wavelength dependency of absorption coefficients in the photoelectric conversion layer itself. Different wavelengths are absorbed at different depths, with blue light absorbed near the surface and red light absorbed deeper, eliminating the need for separate color filters and improving light utilization efficiency while maintaining color separation.
Solution Approach 2:
The patent transitions from planar color separation using color filters to three-dimensional wavelength-based separation using the depth dimension. By utilizing the vertical depth of the photoelectric conversion layer and the wavelength dependency of absorption, the patent achieves color separation in the depth dimension rather than through lateral filtering, thereby capturing more light.
3Productivity
If PD size is reduced for high integration, then pixel density is improved, but light waveguiding into PD becomes difficult
Solution Approach 1:
The patent changes the optical parameters by introducing a light guide layer with specific refractive index between the lens and the photoelectric conversion layer. This parameter change in the optical path compensates for the reduced PD size, improving light coupling efficiency and waveguiding into smaller photodetectors while maintaining high pixel density.
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 improves the external quantum efficiency, reduces dark current, and sharpens spectral sensitivity, preventing the broadening of spectral sensitivity and maintaining high sensitivity across different wavelengths.
Implementation Method 1
a photoelectric conversion layer disposed between the first electrode layer and the second electrode layer... the photoelectric conversion layer generates a charge containing an electron and a hole corresponding to the incident light
Data Source
AI summary
A photoelectric conversion device comprising a photoelectric conversion part including a first electrode layer, a second electrode layer and a photoelectric conversion layer provided between the first electrode layer and the second electrode layer, wherein light is made incident from an upper part of the second electrode layer into the photoelectric conversion layer; the photoelectric conversion layer generates a charge containing an electron and a hole corresponding to the incident light from the upper part of the second electrode layer; and the first electrode layer works as an electrode for extracting the hole.