3D Charge Collection Mapping by Tomographic Probe Beam Scanning
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Solution Overview
Problem
Conventional methods for determining charge collection efficiency in charge carrier-selecting samples, such as solar cells, provide only 2D spatial resolution, lacking depth information necessary for a comprehensive analysis of device performance.
Innovation Solution
A tomographic method that scans a sample with a probe beam and simultaneously measures induced current or voltage, reconstructing a 3D map using tomographic image reconstruction algorithms, allowing for detailed depth analysis by arranging the sample on a stage that moves in three directions and rotates, enabling the creation of a 3D charge collection efficiency map.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a small beam is scanned over the surface of the solar cell to measure charge collection efficiency with spatial resolution, then local performance can be detected, but only 2D spatial resolution is provided without depth information
Solution Approach 1:
The patent applies tomographic reconstruction techniques to transform 2D beam-induced current measurements into 3D charge collection efficiency maps. By scanning the beam across multiple positions and angles, and mathematically reconstructing the data, the method adds the depth dimension to the measurement, enabling visualization of charge collection efficiency throughout the volume of the solar cell rather than just at the surface.
2Reliability
If conventional 2D mapping methods are used to examine charge collection efficiency, then local defects can be identified, but comprehensive 3D analysis of device performance is not achieved
Solution Approach 1:
The patent introduces tomographic reconstruction algorithms as an intermediary processing step between the raw beam-induced current measurements and the final charge collection efficiency maps. This mathematical intermediary transforms the 2D measurement data into 3D visualizations, enabling comprehensive device performance analysis without requiring direct 3D measurement capabilities.
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 method provides a more detailed analysis of the device's performance by incorporating depth information, enabling a deeper understanding of charge collection efficiency variations within the sample volume, which is crucial for identifying local defects and improving device performance.
Implementation Method 1
A tomographic method of determining a 3D map of a charge collection efficiency... in which the sample has a charge carrier selecting structure... measuring the beam induced current and/or voltage
Data Source
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AI summary
A tomographic method of determining a 3D map of a charge collection efficiency in a volume of investigation of a sample and an apparatus for performing the method. The sample has a charge carrier selecting structure and the method comprises the steps of: Arranging the sample in a beam path of a probe beam, wherein the probe beam propagates in a beam-direction which defines an axis in a laboratory frame coordinate system, Scanning the volume of investigation with an analyzing spot of the probe beam and simultaneously measuring the beam induced current and/or voltage, wherein a position of the sample arranged on a sample stage is defined by the coordinates z, y and r and a value of the beam induced current and/or voltage is determined for every position of the sample during the scanning action and Assigning every coordinate point (z, y, r) in the laboratory frame coordinate system, at which the analyzing spot of the probe beam hits the sample to a value of the beam induced current and/or voltage, which is measured for this point (z, y, r), reconstructing the 3D map of the charge collection efficiency by processing the values of the beam induced current and/or voltage determined for the coordinates (z, y, r) in the laboratory frame coordinate system with a tomographic image reconstruction algorithm so as to determine the 3D map of the charge collection efficiency in a coordinate system of the sample.