Search

A fully finished, aluminum back-surface field, multi crystalline silicon solar cell was analyzed using Raman microspectroscopy. New insights into the process and material quality of the finished device is obtained. First, the image scan obtained on the multi crystalline silicon surface is reflective of the textured surface contributing to the surface topology. Second, the analysis helps to identify differences in the Raman spectra of the remnant saw marks on the silicon surface when compared to a textured silicon surface. Third, Raman analysis of the silver line shows a clear silver oxide signal that is detected up to 25 μm away from the edge of the silver line thus, quantifying the quality and effectiveness of the screen-printing and firing process. Finally, inclusions embedded inside the silicon surface are unambiguously identified as nanocrystalline silicon. Using confocal Raman microspectroscopy 3D tomography of the inclusions are constructed and the state of compressive stress around these particulates are measured. Taken together, these results demonstrate Raman microspectroscopy as a valuable tool for identification of micron-scale feature sizes and defects, otherwise too small to be identified using current metrology techniques.

Doped polycrystalline silicon (poly-Si) passivating contacts featuring a thin tunneling oxide have emerged as one of the most promising carrier selective contacts for crystalline silicon (c-Si) solar cells due to their very low recombination and resistive losses, as well as a high thermal stability compared to amorphous silicon (a-Si:H) heterojunctions. This contact technology consists of a heavily doped poly-Si layer on top of a c-Si substrate with an interfacial ultra-thin silicon oxide layer (SiO x ). To implement poly-Si passivating contacts into an industrial silicon solar cell production line, a cost-effective and high-throughput deposition process is required. Atmospheric pressure chemical vapor deposition (APCVD) process is a single side deposition process that requires no vacuum or plasma systems and is very well suited for high volume manufacturing. In this work, we present an in-line APCVD process for depositing heavily phosphorus doped poly-Si films to form low recombination electron contacts using silane (SiH 4 ) and phosphine (PH 3 ) as precursor gases. The as-deposited samples went through different post deposition annealing processes for solid phase crystallization, dopant activation and dopant diffusion. We have studied the effect of different process parameters like deposition temperature, precursor gas ratio and different post deposition treatments etc. on the surface passivation quality of this contact.