Charge Carrier Lifetime Determination Using Control Substrate
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Solution Overview
Problem
Current methods for determining the volume lifetime of charge carriers in semiconductor substrates are complex, hazardous, and require specific passivation processes, making them unsuitable for standard thickness substrates and incompatible with the photovoltaic industry's requirements.
Innovation Solution
A method involving the use of passivated sample substrates with characterized recombination rates, utilizing a control substrate with known volume lifetime to determine the volume lifetime of the sample substrate without removing or replacing passivation structures, allowing for measurement at any time after passivation, and applicable to substrates with standard thicknesses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional passivation methods using hydrofluoric acid are used to measure volume lifetime, then the measurement accuracy is improved, but the process complexity and safety hazards increase significantly
Solution Approach 1:
The patent uses a disposable control substrate with pre-formed passivation structures instead of requiring complex passivation processes on measurement substrates. The control substrate is used once to characterize the passivation structure and then discarded, eliminating the need for hazardous chemical passivation steps in subsequent measurements while maintaining measurement accuracy.
Solution Approach 2:
The patent creates a copy of the passivation structure on a control substrate that can be characterized separately. By measuring the effective lifetime on the control substrate with known volume lifetime, the recombination rate of the passivation structure is determined and can be applied to measure volume lifetime on measurement substrates without direct passivation, thus simplifying the measurement process.
2Reliability
If substrates are thinned to measure volume lifetime using traditional methods, then the measurement reliability is improved, but the substrate thickness requirement becomes incompatible with standard photovoltaic industry specifications
Solution Approach 1:
The patent transfers the measurement function to a control substrate with known properties. By characterizing the passivation structure on the control substrate and using it to determine the recombination rate, the method enables volume lifetime measurement on standard-thickness substrates without requiring substrate thinning, thus maintaining both reliability and compatibility with industry standards.
Solution Approach 2:
The patent changes the measurement approach from direct measurement on thinned substrates to indirect measurement using effective lifetime on passivated substrates with known recombination rates. This parameter transformation allows volume lifetime to be determined from effective lifetime measurements on substrates of any thickness, eliminating the thinning requirement.
3Measurement precision
If immediate measurement after illumination is performed to reduce passivation degradation, then the measurement precision is improved, but the device complexity and operational difficulty increase
Solution Approach 1:
The patent performs preliminary characterization of the passivation structure on a control substrate to determine its recombination rate before using it for measurements. This preliminary action creates a reference that can be used for subsequent measurements without time constraints, eliminating the need for immediate measurement after illumination and simplifying the operational procedure.
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
Enables simple, rapid, and safe determination of volume lifetime, compatible with standard substrate thicknesses, and compatible with the photovoltaic industry's processes, reducing complexity and hazards associated with hazardous passivating solutions.
Implementation Method 1
supplying a passivated sample substrate with means of a first passivation structure arranged on a first face of the sample substrate and a second passivation structure arranged on a second face of the sample substrate
Implementation Method 2
The effective lifetime of charge carriers is measured by decay of the photoconductance signal
Data Source
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AI summary
One aspect of the invention relates to a method for determining (100) the volumetric lifetime of charge carriers of a sample substrate (1) passivated by means of passivation structures, comprising: - a step of characterizing (110) a recombination rate (S) associated with the passivation structures from a control substrate (2) passivated by means of the passivation structures and having a known volumetric lifetime of charge carriers; - a step of measuring (122) the effective lifetime of charge carriers (τ1) of the sample substrate (1); - a step of determining (123) the volumetric lifetime of charge carriers of the sample substrate (1) from the effective lifetime of charge carriers (τ1) and the recombination rate (S) associated with the passivation structures.