A novel, scalable, and low-cost strategy for fabricating sub-wavelength scale hierarchical nanostructures by direct patterning of TiO 2 nanoparticles on glass substrates is reported. Two nanostructural designs of light-trapping back-surface reflectors (BSR) have been fabricated for increasing the photon-harvesting properties of thin-film solar cells: a quasi-periodic nano-crater design and a random nano-bump design. The efficient light-scattering properties of the nano-crater design over a broad wavelength range are demonstrated by the measured haze factor being larger than 40% at wavelengths (~ 700 nm) near the band edge of amorphous silicon (a-Si: H). The a-Si: H-based nip solar cell fabricated with an only~ 200 nm thick absorber layer on the nano-crater BSR shows a short-circuit current density (J sc) of~ 16.1 mA cm− 2 representing a 28% enhancement compared to the cell deposited on a non-textured flat …