Hexagonal microtextured glass to achieve high optical performance in thin-film silicon solar cells

Periodic hexagonal microtexture arrays (also known as honeycombs) are successfully implemented for the first time in a superstrate glass configuration. Hexagonal textures on glass demonstrate an anti-reflective effect when compared to flat glass. It is shown that light scattering increases at the honeycomb interfaces with an increase in texture height and periodicity. The performance of the textures is demonstrated using thin-film single-junction PV devices based on an indirect bandgap semiconductor material, nanocrystalline silicon (nc-Si:H), which requires light trapping in the infrared region of the spectrum. Inspecting the nc-Si:H bulk absorber suggests a conformal, crack-free growth of crystals on the hexagonal arrays. Short-circuit current density ( J S C ) increases with an increase in the aspect ratio of the superstrate, without compromising voltage and fill factor. The J S C enhancement is attributed to a combined benefit of (i) the anti-reflective nature of developed textures, (ii) trapping light within the absorbing layer through multiple order diffraction at the front and (iii) reflection from a back reflector with adapted hexagonal morphology. With the above observations, a J S C of 28.6 mA/cm 2 (photovoltaic conversion efficiency of 9.3 %) is achieved for a 5 μ m periodic texture with a height of 1 μ m (aspect ratio = 0.21). This is the highest reported J S C for a single-junction nc-Si:H solar cell in a superstrate configuration without an external anti-reflection coating. • Periodic hexagonal micro-texture arrays on glass are successfully implemented for the first time in a superstrate configuration. • With increased texture height and periodicity, light scattering at texture interfaces is enhanced. • Hexagonal arrays facilitate conformal, crack-free growth of silicon crystals on glass. • The short-circuit current of 28.60 mA/cm 2 is the highest reported for a single-junction nanocrystalline silicon solar cell without an anti-reflection coating.