Light-Harvesting Properties of Embedded Tin Oxide Nanoparticles for Partial Rear Contact Silicon Solar Cells

In this paper, a novel method of preparation and systematic study of application of low-loss tin oxide (SnO₂) nanospheres located at the rear side of crystalline silicon solar cells having partial rear contact have been presented. The improvement in efficiency due to light harvesting through optical scattering of tin oxide nanospheres is significant for thin silicon solar cells. Finite-difference time-domain (FDTD) simulations reveal that embedding of the rear-located nanospheres is necessary for back scattering of light from the rear surface. An analytical electrical model has been developed utilizing the results of optical simulations to estimate the solar cell parameters and efficiency enhancement of solar cells. The model shows that an absolute efficiency enhancement of ～19% can be achieved for 16% efficient 10-μm thin silicon solar cell with partial rear contact. The enhancement is lower (～6%) for thicker (180 μm) partial rear contact cells. Experimentally, SnO₂ nanospheres have been synthesized and applied at the rear side of partial rear contact solar cell as a proof of experiment to validate the potential of this approach. A relative enhancement of short-circuit current by 2.3% and open-circuit voltage by 2.5% has been achieved experimentally for 180-μm silicon solar cells leading to 5.2% higher efficiency with respect to baseline efficiency validating this concept.