Solid-State Imaging Device With Charge Blocking Layer
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Solution Overview
Problem
Solid-state imaging devices face challenges with reduced pixel aperture ratio due to increased circuit area, leading to decreased sensitivity, and existing techniques fail to effectively control dark current and color cross-talk.
Innovation Solution
A solid-state imaging device with a photoelectric layer containing p-type and n-type organic semiconductors, a charge blocking layer with specific ionization potential and electron affinity differences, and a transparent partition wall between color filters to reduce dark current and improve signal-to-noise ratio while preventing color cross-talk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pixel pitch is reduced to increase pixel density, then the pixel aperture ratio decreases due to larger circuit area occupation, but sensitivity is improved through better pixel packing
Solution Approach 1:
The patent transitions from a planar pixel structure to a three-dimensional stacked structure by introducing a photoelectric layer extending vertically from the substrate. This allows light detection in the vertical dimension while keeping the horizontal pixel pitch small, thereby maintaining high pixel density without sacrificing aperture ratio. The photoelectric layer's vertical extension enables effective light collection area to increase without increasing the horizontal footprint.
2Reliability
If a charge blocking layer is added to reduce dark current, then the signal-to-noise ratio is improved, but the device complexity increases
Solution Approach 1:
The patent optimizes the charge blocking layer by carefully selecting materials with specific energy level parameters - the ionization potential should be at least 1 eV higher than the HOMO level of the organic semiconductor, and the electron affinity should be at least 1 eV lower than the LUMO level. This parameter-based approach enables effective dark current suppression through controlled charge injection barriers while maintaining a relatively simple single-layer structure.
3Object-affected harmful factors
If the photoelectric layer thickness is reduced to minimize optical cross-talk, then color cross-talk is reduced, but light absorption efficiency decreases
Solution Approach 1:
The patent employs composite organic semiconductor materials with high absorption coefficients in the visible range. By combining materials that exhibit strong light absorption properties with appropriate energy level alignments, the system achieves effective light capture in thin films. The composite approach allows simultaneous optimization of both light absorption efficiency and optical isolation through careful material selection rather than relying solely on thickness control.
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 effectively reduces dark current, enhances signal-to-noise ratio, and minimizes color cross-talk by optimizing the charge blocking layer and partition wall design, improving light collection and image quality.
Implementation Method 1
the organic layer 107 has a photoelectric layer 12 generating charges in response to light received
Implementation Method 2
a charge blocking layer 15 being provided between the photoelectric layer 12 and at least one of the pixel electrode 104 and the counter electrode 108 and blocking charge injection from the pixel electrode 104 and/or the counter electrode 108 to the photoelectric layer 12
Implementation Method 3
The partition wall is of a material having a lower refractive index than the material of the color filters
Data Source
AI summary
A solid state imaging device includes an array of pixels, each of the pixels includes: a pixel electrode; an organic layer; a counter electrode; a sealing layer; a color filter; and a readout circuit as defined herein, the photoelectric layer contains an organic p type semiconductor and an organic n type semiconductor, an ionization potential of the charge blocking layer and an electron affinity of the organic n type semiconductor in the photoelectric layer have a difference of at least 1 eV, and the solid-state imaging device further includes a transparent partition wall between adjacent color filters of adjacent pixels of the array of pixels, the partition wall being made from a transparent material having a lower refractive index than a material forming the color filters.