Solid state interdigitated Sb₂S₃ based TiO₂ nanotube solar cells

TiO₂ nanotubes generated by anodization of metallic titanium sputter-coated on indium tin oxide (ITO) substrates are used as a conductive scaffold for all solid-state Sb₂S₃-sensitized extremely thin absorber (ETA) solar cells. A blocking layer of TiO₂ placed between Ti and ITO in combination with optimized Ti deposition and anodization conditions enables the formation of crack-free layers of straight, cylindrical TiO₂ nanotubes of tunable length and diameter. ALD (atomic layer deposition) is subsequently used to coat this substrate conformally with a highly pure Sb₂S₃ light absorber layer under an inert atmosphere. The high absorption coefficient of Sb₂S₃ as compared to molecular dyes allows for the utilization of very short nanotubes, which facilitates the infiltration of the organic hole transport material and formation of a p-i-n heterojunction in an interdigitated and tunable geometry. We investigate the influence of nanotube length and of the absorber thickness to enhance the photocurrent value to twice that of planar reference structures.