Shunt-analysis of epitaxial silicon thin-film solar cells by lock-in thermography

Lock-in thermography has been applied for shunt-analysis on epitaxial silicon thin-film solar cells. The solar cell material was made by epitaxial deposition of the base layer on highly doped monocrystalline (Czochralski) and multicrystalline silicon substrates in an APCVD-system. Solar cells were prepared in a laboratory-type and an industrial-type process. Characterization of the solar cells by infrared lock-in thermography and microscopy revealed a clear correlation between shunts and epitaxial defects in case of the lab-type solar cells. Furthermore an increased concentration of shunts located under the emitter grid lines of the industrial-type solar cells compared to the lab-type solar cells was observed. The analysis by thermography thus gave insight into the quality of the epitaxial layers and into problems concerning a transfer of the solar cell process from laboratory to industrial scale manufacturing.