Standard Cameras Modified to Measure Solar Cell Quantum Efficiency

Researchers at the University of Stuttgart, Research Center Juelich, and Solarzentrum Stuttgart have demonstrated that commercially available cameras, with minor hardware modifications, can provide quantitative measurements of solar cell efficiency through electroluminescence imaging - a technique previously requiring specialised laboratory equipment.

The study, published in The Journal of Applied Physics by AIP Publishing, shows that a standard silicon camera already lacking an infrared-blocking filter can be further adapted with a long-pass filter to reduce visible background light. The resulting instrument can then analyse electroluminescence images based on pixel brightness values to extract absolute luminescent quantum efficiency data.

Electroluminescence imaging works by applying a voltage to a solar cell and recording the light it emits. Regions of high local efficiency appear brighter; defects or degraded areas appear darker. The technique has long been used qualitatively, but extracting absolute efficiency values has typically required calibrated scientific instruments.

"An electroluminescence image contains much more quantitative information than simply showing bright and dark regions," said lead author Juergen Werner. With the calibrated camera, researchers can determine both absolute luminescent quantum efficiency and local solar cell quality across the full cell area in a single image.

Luminescent quantum efficiency is directly linked to the open-circuit voltage of a solar cell, one of the key parameters determining overall power conversion performance. Mapping it spatially allows identification of efficiency losses at specific locations within the cell, informing quality control and cell optimisation.

Werner described the next phase of the work: "Our next step is to use the calibrated camera to determine quantum efficiencies and open-circuit voltages of further, previously uncharacterised solar cells." The approach could lower the cost and complexity of cell characterisation for both research and manufacturing contexts.

The paper, "New Camera Model for Absolute Quantum Efficiency Measurements from Electroluminescence of Solar Cells or Modules," is authored by Juergen H. Werner, Georgette Udo, and Liviu Stoicescu.

CONTACT: https://doi.org/10.1063/5.0349589