Vertical PbS Infrared Sensor Structure for Faster Low-Light Detection
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Solution Overview
Problem
Conventional silicon-based image sensors exhibit insufficient light conversion efficiency for long-wavelength light and inadequate low-light sensing capability, and planar thin film transistors using lead sulfide quantum dots require high driving voltages and suffer from response time delays and conductivity issues due to vacancies at carrier transfer interfaces.
Innovation Solution
A vertical light sensing element is developed with a substrate, a first electrode, and a light-sensing unit comprising sequentially stacked zinc oxide (ZnO)-based, halide ion-modified, and thiol-modified lead sulfide (PbS)-based layers, along with a second electrode to form a current flow path, enhancing electron transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If PbS-QDs are used as light sensing material in planar thin film transistor, then light conversion efficiency for long-wavelength light is improved, but driving voltage increases and response time delays
Solution Approach 1:
The patent transitions from a planar thin film transistor structure to a vertical light sensing element structure. This dimensional change allows the light sensing material PbS-QDs to be positioned vertically between electrodes, reducing the horizontal distance carriers must travel and enabling faster response while maintaining long-wavelength detection capability
Solution Approach 2:
The patent modifies the electrode configuration and structural geometry of the light sensing element. By changing from planar to vertical arrangement, the physical parameters such as electrode distance and carrier transport path are optimized, achieving both high light conversion efficiency and fast response time
2Loss of time
If vertical light sensing element is developed, then response time is reduced, but vacancies exist on carrier transfer interface affecting conductivity
Solution Approach 1:
The patent introduces a ZnO-based layer as an intermediary between the PbS-QDs and other materials at the carrier transfer interface. This intermediate layer fills and passivates vacancies, improving interfacial contact and overall conductivity while preserving the fast response characteristics of the vertical structure
Solution Approach 2:
The patent creates a composite structure combining PbS-QDs with ZnO-based materials and other functional layers. This composite approach addresses the conductivity issue by integrating materials with complementary properties, where ZnO fills vacancies and enhances interfacial charge transfer while PbS-QDs maintain light sensing performance
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 conversion efficiency and reduces response time by minimizing surface defects and vacancies, resulting in enhanced responsivity and detectivity of the infrared sensor.
Implementation Method 1
The light-sensing unit is disposed on a surface of the first electrode opposite to the substrate, is capable of absorbing and sensing infrared light
Implementation Method 2
The first PbS-based modification layer includes halide ion-modified PbS
Implementation Method 3
the second PbS-based modification layer includes thiol-modified PbS
Data Source
AI summary
An infrared sensor includes a substrate, a first electrode, a light-sensing unit, and a second electrode. The substrate is infrared-transmissible. The first electrode is disposed on a surface of the substrate and is infrared-transmissible. The light-sensing unit is disposed on a surface of the first electrode opposite to the substrate, is capable of absorbing and sensing infrared light, and includes a zinc oxide (ZnO)-based layer, a first lead sulfide (PbS)-based modification layer, and a second PbS-based modification layer that are sequentially stacked from the surface of the first electrode. The first PbS-based modification layer includes halide ion-modified PbS, and the second PbS-based modification layer includes thiol-modified PbS. In addition, the second electrode is disposed on a surface of the light-sensing unit opposite to the substrate, and is capable of forming a current flow path by cooperating with the light-sensing unit and the first electrode.