Solar Cell Efficiency Mapping
A custom laser-scanning rig that maps where a silicon solar cell loses current, matched against microscope images of deliberately introduced defects. Each type of damage leaves a distinguishable electrical signature, validating the method as a non-destructive inspection tool.
Team
Hee Hwang (lead), Brian Cho, Chanju Park, Kyuwon Lee, Sunghyo Byoun, Chloe Lee — Materials Science & Engineering, Electrical & Computer Engineering, Computer Science, and the School of Information Sciences.
Question
Does damage you can see on a solar cell’s surface actually cost measurable power? Most inspection methods need electrical contacts or run too slowly for rapid screening, so we built our own and tested the correlation directly.
What we built
- A Light Beam Induced Current (LBIC) scanner: a 650 nm laser on a motorized XY stage stepping in 0.1 mm increments, measuring current point by point across a cell and turning it into a spatial response map.
- Controlled damage introduced by pressing an indenter between the cell’s metal fingers, with the force varied to produce defects of different severity.
- Optical microscope images of the same cells, aligned to the current maps so visible damage can be compared against electrical loss.
Findings
- Damaged spots appear as clear low-response regions — the loss is real and localized.
- Different kinds of damage leave different electrical signatures, pointing to different failure mechanisms.
- The maps and the microscope images agree on where the defects are, which is what makes the method usable as a diagnostic.
Next steps
Automatic defect classification, predicting cell performance from images alone, and scaling to larger-area devices.
Presented
MRC 2026 and Engineering Open House 2026, University of Illinois Urbana-Champaign.
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