Quantum-Dot Photodetector Layers for Lower Infrared Dark Current
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Photodetector elements using silicon photodiodes have low sensitivity in the infrared region and InGaAs-based materials require high-cost processes, while photodetector elements with semiconductor quantum dots exhibit high dark current, limiting their performance in image sensors.
Innovation Solution
A photodetector element design incorporating a photoelectric conversion layer with semiconductor quantum dots containing a metal atom and a coordinated ligand, paired with a hole transport layer of semiconductor quantum dots having a larger band gap, reduces dark current by optimizing the band gap difference and energy levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If semiconductor quantum dots are used as photoelectric conversion layer, then infrared sensitivity is improved, but dark current increases
Solution Approach 1:
The patent applies local quality by creating distinct regions with different quantum dot characteristics: the photoelectric conversion layer uses quantum dots optimized for infrared absorption, while the hole transport layer uses quantum dots with larger band gaps optimized for hole transport. This spatial differentiation of material properties allows each layer to perform its specific function optimally while the hole transport layer's larger band gap suppresses dark current generation.
Solution Approach 2:
The patent employs composite materials by combining two types of semiconductor quantum dots with different band gap characteristics into a layered structure. The composite system integrates infrared-sensitive quantum dots in the photoelectric conversion layer with larger band gap quantum dots in the hole transport layer, achieving both high infrared sensitivity and low dark current through the synergistic combination of different material properties.
2Reliability
If InGaAs-based semiconductor material is used, then quantum efficiency is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive InGaAs-based semiconductor materials with semiconductor quantum dots that can be manufactured using lower-cost processes. The quantum dot-based photodetector element achieves comparable or superior performance through solution processing and simplified fabrication techniques, effectively substituting high-cost epitaxial growth materials with more economical quantum dot structures.
Solution Approach 2:
The patent changes the material parameter from bulk InGaAs semiconductor to nanoscale semiconductor quantum dots, fundamentally altering the manufacturing approach. This parameter change enables the use of solution-based processing and simpler fabrication techniques instead of expensive epitaxial growth, reducing manufacturing costs while maintaining or improving quantum efficiency through quantum confinement effects.
3Ease of manufacture
If silicon photodiode is used, then manufacturing is simplified, but infrared sensitivity deteriorates
Solution Approach 1:
The patent changes the fundamental material parameter from bulk silicon to nanoscale semiconductor quantum dots, which fundamentally alters the optical properties. The quantum confinement effect in nanoscale quantum dots enables tuning of the absorption spectrum to extend into the infrared region, overcoming silicon's intrinsic infrared transparency while maintaining compatibility with simplified manufacturing processes.
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 achieves a photodetector element with reduced dark current, enhancing the signal-to-noise ratio and performance of image sensors, particularly in infrared imaging.
Implementation Method 1
a photodetector element having a photoelectric conversion layer that contains semiconductor quantum dots
Implementation Method 2
containing a ligand that is coordinated to the semiconductor quantum dot
Data Source
AI summary
There is provided a photodetector element having a photoelectric conversion layer containing an aggregate of semiconductor quantum dots QD1 that contain a metal atom and containing a ligand L1 that is coordinated to the semiconductor quantum dot QD1, and a hole transport layer containing an aggregate of semiconductor quantum dots QD2 that contains a metal atom and containing a ligand L2 that is coordinated to the semiconductor quantum dot QD2, the hole transport layer being arranged on the photoelectric conversion layer, in which a band gap Eg2 of the semiconductor quantum dot QD2 is larger than a band gap Eg1 of the semiconductor quantum dot QD1, and a difference between the band gap Eg2 of the semiconductor quantum dot QD2 and the band gap Eg1 of the semiconductor quantum dot QD1 is 0.10 eV or more. There is also provided an image sensor including the photodetector element.