Combinatorial Investigation and Modelling of MoO₃ Hole-Selective Contact in TiO₂|Co₃O₄|MoO₃ All-Oxide Solar Cells

A TiO₂|Co₃O₄|MoO₃ all-oxide solar cell produced by spray pyrolysis and pulsed laser deposition (PLD) onto a fluorine-doped tin-oxide (FTO) glass substrate with gold (Au) back contacts is demonstrated for the first time. A combinatorial approach is implemented to study the effect of molybdenum oxide (MoO₃) as a recombination contact and the influence of the cobalt oxide (Co₃O₄) light-absorber thickness on the performance of the solar cells. An increase of more than 200 mV in the open circuit voltage (V_oc) is observed with a concurrent enhancement in terms of short-circuit current (J_sc) and maximum power in comparison with TiO₂|Co₃O₄ devices without the MoO₃ layer. To understand the mechanism, full drift diffusion simulations are performed. The higher performance is attributed to elimination of a recombination process at the absorber/metal back-contact interface and surface passivation by the MoO₃ layer.