SRI
The SRI system (Sheet Resistance Imaging) which was developed in cooperation with the Fraunhofer ISE research institute is a solution for fast spatially resolved sheet resistance imaging before and after emitter diffusion. The principle of free carrier absorption in combination with a fast, high precision CCD camera, sensitive in the infrared is used to establish a measurement method for determining the emitter sheet resistance of silicon solar cells.
A infrared mirror with a surface reflecting the relatively cold background temperature of the housing is heating up a wafer sample, so that it radiates with a black body spectrum due to the sample´s temperature. The signal is approximately proportional to the density of free carriers. The density is related to the doping level. By calculating the difference between a measurement before and after emitter diffusion, a spatially resolved emitter Sheet Resistance Image (SRI) may be obtained by an appropriate calibration. With this new setup a fast, contactless quality control of the diffusion process in wafer and solar cell production is possible.
Technical Specification
- Fast, high precision IR camera with high resolution
- Cell size up to 156x156 mm (Modell SRI 156) or up to 210x210 mm (Modell CSRI 210)
- Non-destructive and contactless measurement
- Measurement time less than 10 seconds
- Spatial resolution of a 100x100 mm wafer approximately 390 μm
- CDI, ILIT and SRI also available in combination as IR-Multitool 210