AgBiS2 Nanoparticle Light-Receiving Layer for Near-Infrared Detection
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Solution Overview
Problem
Current semiconductor materials struggle to respond effectively to near-infrared light, particularly in applications like LIDAR and SWIR image sensors, due to limitations in band gap values and environmental concerns associated with existing materials like PbS.
Innovation Solution
Development of a photoelectric conversion element material with a light-receiving layer composed of Ag2−xBixSx+1 semiconductor nanoparticles, where the crystallite diameter is controlled between 10 nm and 25 nm to enhance responsiveness to near-infrared light, using AgBiS2 or Ag2S as the metal chalcogenide, which are dispersed in an ink and applied to a base material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional semiconductor materials like silicon are used, then the device structure is simple and manufacturing is easy, but the responsiveness to near-infrared light is insufficient due to band gap limitations
Solution Approach 1:
The invention changes the fundamental material parameter (band gap) by transitioning from silicon-based semiconductors to metal chalcogenide nanoparticles (CdSe, CdTe, PbS, PbSe, Ag2S, AgBiS2). This material substitution enables the light-receiving layer to respond to near-infrared wavelengths that conventional silicon cannot detect, directly resolving the contradiction between maintaining simple device structure and achieving extended wavelength responsiveness.
Solution Approach 2:
The invention employs composite material structures by combining metal chalcogenide nanoparticles with organic ligands and encapsulating them in a light-receiving layer matrix. This composite approach allows the integration of nanoparticles with tailored band gap properties into a functional device structure, achieving both near-infrared responsiveness and structural integrity.
2Reliability
If PbS semiconductor nanoparticles are used to achieve near-infrared responsiveness, then photoresponsivity improves, but environmental harm increases due to lead content
Solution Approach 1:
The invention extracts and removes the harmful lead component from the semiconductor material system by replacing PbS and PbSe nanoparticles with lead-free alternatives such as Ag2S and AgBiS2. This substitution maintains the desired near-infrared photoresponsivity while eliminating the environmental toxicity associated with lead-containing materials.
Solution Approach 2:
The invention adopts alternative semiconductor materials (Ag2S, AgBiS2) that are environmentally benign and can be synthesized through cost-effective wet chemical methods. These materials provide the necessary optical properties without the environmental burden of lead, enabling sustainable photoelectric conversion applications.
3Length of moving object
If semiconductor nanoparticle thickness is reduced below 1 μm to enable size reduction, then device miniaturization is achieved, but manufacturing precision requirements increase
Solution Approach 1:
The invention introduces organic ligands (oleic acid, oleylamine, hexadecylamine) as intermediary molecules that adsorb onto the nanoparticle surfaces and provide steric stabilization. These ligands prevent nanoparticle aggregation during thin film formation, enabling precise control of layer thickness at sub-micron scales while maintaining manufacturing feasibility through solution processing.
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 material exhibits improved photoresponsivity and light sensitivity in the near-infrared region, outperforming conventional materials like PbS, and is suitable for applications in LIDAR and SWIR image sensors, with the crystallite diameter optimization crucial for maintaining high responsiveness.
Implementation Method 1
semiconductor nanoparticles that are referred to as quantum dots (QDs) is expected. Semiconductors develop a quantum confinement effect when being composed of nano-scale fine particles and have a band gap based on the particle diameters
Implementation Method 2
Semiconductors develop a quantum confinement effect when being composed of nano-scale fine particles and have a band gap based on the particle diameters. Therefore, the adjustment of the band gap by controlling the composition and particle diameters of semiconductor nanoparticles makes it possible to arbitrarily set light-emitting wavelengths or absorption wavelengths
Data Source
AI summary
The present invention relates to a photoelectric conversion element material provided with a base material and a light-receiving layer including a semiconductor film formed on the base material. The semiconductor film that forms this light-receiving layer includes Ag2−xBixSx+1 (x is an integer of 0 or 1) and has a crystallite diameter of 10 nm or more and 40 nm or less. The light-receiving layer can be produced by applying an ink containing the semiconductor nanoparticles dispersed in a dispersion medium to a base material and then firing the ink at 200° C. or higher and 350° C. or lower. The photoelectric conversion element material of the present invention has an absorption property with respect to light with wavelengths in the near infrared region and excellent photoresponsivity.