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Optical technique for photovoltaic spatial current response measurements using compressive sensing and random binary projections
Compressive sensing has been widely used in image compression and signal recovery techniques in recent years; however, it has received limited attention in the field of optical measurement. This paper describes the use of compressive sensing for measurements of photovoltaic (PV) solar cells, using fully random sensing matrices, rather than mapping an orthogonal basis set directly. Existing compressive sensing systems optically image the surface of the object under test, this contrasts with the method described, where illumination patterns defined by precalculated sensing matrices, probe PV devices. We discuss the use of spatially modulated light fields to probe a PV sample to produce a photocurrent map of the optical response. This allows for faster measurements than would be possible using traditional translational laser beam induced current techniques. Results produced to a 90% correlation to raster scanned measurements, which can be achieved with under 25% of the conventionally required number of data points. In addition, both crack and spot type defects are detected at resolutions comparable to electroluminescence techniques, with 50% of the number of measurements required for a conventional scan.
This work was funded through the European Metrology Research Programme (EMRP) Project ENG55 PhotoClass. The EMRP is jointly funded by the EMRP participating countries within EURAMETand the European Union. This work is co-funded by the UK National Measurement System. This work was supported in part by the Research Councils UK (RCUK) through the project “Stability and Performance of Photovoltaics (STAPP)” (contract no: EP/H040331/1).
- Mechanical, Electrical and Manufacturing Engineering