Combined Thermography and Luminescence Imaging to Characterize the Spatial Performance of Multicrystalline Si Wafer Solar Cells

As-cut partially processed multicrystalline Si (mc-Si) wafers and complete mc-Si solar cells are characterized using photoluminescence imaging, defect mapping, and thermographic local current-voltage (I-V) analysis. Photoluminescence imaging applied to the partially processed mc-Si material after 1) RCA clean and a surface damage etch, 2) diffusion and phosphate silica glass removal, and 3) SiN_x:H coating reveals local performance enhancements over regions of the mc-Si wafer solar cell. A comprehensive imaging study including defect luminescence imaging, polarization imaging, breakdown imaging, and dark lock-in thermography is applied to the final device after metallization to obtain defect distributions and local spatially resolved I-V characteristics of the device. The analysis shows that substrate defects, reverse-bias, and subbandgap electroluminescence emission from various defects in the device correlate spatially with the determined electrical properties of the device.