Multijunction Solar Cell Characterization via Spectral Segmentation
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Solution Overview
Problem
Current techniques for characterizing multijunction solar cells are inefficient in measuring individual subcell performance metrics due to series connection limitations, leading to unpredictable results from subjective light and voltage bias settings, and require complex spectral mismatch corrections.
Innovation Solution
An apparatus and method that control light intensity for each subcell spectral range while maintaining constant intensity for others, using optical filters and beam combiners to measure current-voltage data, allowing for precise determination of subcell parameters like open circuit voltage, short-circuit current, and quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If monochromatic light is used to measure quantum efficiency of multijunction solar cells, then the measurement can be performed with a simple setup, but the other subcells generate no photocurrent due to spectral mismatch, resulting in no overall photocurrent
Solution Approach 1:
The patent divides the broadband light spectrum into multiple wavelength bands, each corresponding to a specific subcell's spectral response range. By segmenting the light source into wavelength-specific components, the system can selectively illuminate individual subcells while maintaining series connection, enabling independent characterization of each subcell's quantum efficiency without requiring complex spectral mismatch corrections
Solution Approach 2:
The patent introduces an optical filter as an intermediary component between the broadband light source and the multijunction solar cell. The optical filter selectively transmits specific wavelength ranges that correspond to the spectral response of individual subcells, enabling precise control over which subcell is being characterized while blocking wavelengths that would not contribute to that subcell's photocurrent generation
2Measurement precision
If light bias and voltage bias are applied to non-probed subcells during quantum efficiency measurement, then individual subcell QE can be measured, but the choice of bias settings affects results unpredictably and requires subjective optimization
Solution Approach 1:
The patent extracts and removes the need for subjective light and voltage bias optimization by using optical filters to selectively block wavelengths that would otherwise require biasing to prevent spectral mismatch issues. This eliminates the unpredictable effects of bias setting choices and provides a straightforward measurement procedure
Solution Approach 2:
The measurement system uses the multijunction solar cell's own spectral response characteristics to automatically determine the appropriate wavelength ranges for illuminating each subcell. The system self-adjusts by selecting wavelength bands that naturally correspond to each subcell's absorption spectrum, eliminating the need for external bias optimization
3Device complexity
If the spectral response range of the light source does not match the subcell spectral range, then measurement setup is simpler, but the measured performance metrics are inaccurate due to spectral mismatch
Solution Approach 1:
The patent implements dynamic wavelength selection by using optical filters that can be adjusted or selected based on which subcell is being characterized. The system dynamically adapts the spectral content of the illuminating light to match the specific spectral response requirements of each subcell, ensuring accurate performance metric measurement while maintaining a relatively simple overall setup
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 accurate characterization of individual subcells, reducing errors and optimizing multijunction solar cell performance by providing reliable and reproducible measurement of performance metrics.
Implementation Method 1
Photovoltaic solar cells are used to convert sunlight energy into electricity by absorbing, using semiconductor materials, photons having an energy larger than the semiconductor bandgap, the absorption of photons causing the generation of photocarriers (electrons and holes)
Implementation Method 2
The light-control system can comprise a series of optical filters, each optical filter to transmit one of the one or more light beams at a respective transmission intensity corresponding to one of the varied intensities
Data Source
AI summary
An apparatus to electrically and optically characterize a multijunction solar cell. The apparatus can have as many light sources as there are subcells in the multijunction solar cell. Each light source has an optical spectrum that falls within the bandgap energy of a corresponding subcell. Each light source has a controllable intensity level.