LBIC Mapping System
Features:
- Calibrated maps of the
- external quantum efficiency (EQE),
- reflection coefficient (R),
- internal quantum efficiency (IQE) - 826 nm wavelength
- 6 µm spatial resolution
- Measurement time typically 10 - 20 ms / point at a signal-to-noise-ratio of about 200
- Reproducability of the measured values in the order of 5 promille
A typical map with about 500 x 500 measurement points takes between 1 and 2 hours.
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An example of an LBIC map measured on an older multicrystalline silicon solar cell with 50 µm resolution is shown below. Red colors correspond to good regions of the cell. Blue and dark colors show bad performing areas with enhanced recombination of minority carriers. The left and upper border of the sample is deteriorated by impurities like iron that diffused into the solid silicon from the crucible after crystallization when the silicon was still hot. These impurities can form precipitates and can even settle down at extended defects like grain boundaries or dislocations.
Grain boundaries are visible as random shaped lines. Dislocation clusters produce typically blurred structures. The horizontal and vertical thick black lines are due to shading of the contact grid of the solar cell.
Todays multicrystalline solar cells are less limited by such defects due to strong research and development during the last years.
