Hierarchical Etching for Improved Optical Front-side Properties of Monocrystalline Si Solar Cells

Frank Heinemeyer, Verena Steckenreiter, Fabian Kiefer, Robby Peibst
2015 Energy Procedia  
We investigate a hierarchical surface structuring process to reduce the optical reflectance of monocrystalline Si solar cells to below the reflectance of state-of-the-art alkaline texturing. First, alkaline texturing is performed, yielding random pyramids with a few micrometers in size. Second, plasma etching forms step-shaped structures smaller than the wavelength of visible light. Eventually, the surface morphology is formed by <111> planes with many steps, edges and inverted pyramids in a
more » ... ed pyramids in a few hundreds of nanometers scale. We investigate the reflectance on double-side textured samples with SiN x /Al 2 O 3 front-side and SiN x rearside passivation. These dielectric stacks exhibit a low reflectance for conventional alkaline textured surfaces. The short circuit current density potential of the best hierarchical structured samples is 0.4 mA/cm 2 higher when integrating the AM1.5G spectrum from 300 nm to 1000 nm. Furthermore, our results suggest that structures with dimensions smaller than the thickness of an antireflection-and passivation (AR) layer cannot be covered conformal by the AR layer when using plasma-enhanced chemical vapor deposition. Thus, there seems to be a lower limit for the structure size, and wet chemical cleaning sequences -performed after plasma etching -have to be adjusted accordingly.
doi:10.1016/j.egypro.2015.07.114 fatcat:qtleqs5dt5c4pon5hgku34khbe