Here we present for the first time a TiO2/Cu2O all-oxide heterojunction solar cell entirely produced by spray pyrolysis onto fluorine doped tin oxide (FTO) covered glass substrates, using silver as a back contact. A combinatorial approach was chosen to investigate the impact of the TiO2 window layer and the Cu2O light absorber thicknesses. We observe an open circuit voltage up to 350mV and a short circuit current density which is strongly dependent of the Cu2O thickness, reaching a maximum of {\~{}}0.4mA/cm2. Optical investigation reveals that a thickness of 300nm spray pyrolysis deposited Cu2O is sufficient to absorb most photons with an energy above the symmetry allowed optical transition of 2.5eV, indicating that the low current densities are caused by strong recombination in the absorber that consists of small Cu2O grains.

This paper presents the performance of a passive planar rhombic micromixer with diamond-shaped obstacles and a rectangular contraction between the rhombi. The device was experimentally optimized using water for high mixing efficiency and a low pressure drop over a wide range of Reynolds numbers (Re = 0.1–117.6) by varying geometrical parameters such as the number of rhombi, the distance between obstacles and the contraction width. Due to the large amount of data generated, statistical methods were used to facilitate and improve the results of the analysis. The results revealed a rank of factors influencing mixing efficiency: Reynolds number {\textgreater} number of rhombi {\textgreater} contraction width {\textgreater} inter-obstacles distance. The pressure drop measured after three rhombi depends mainly on Re and inter-obstacle distance. The resulting optimum geometry for the low Re regime has a contraction width of 101 $μ$m and inter-obstacles distance of 93 $μ$m, while for the high Re regime a contraction width of 400 $μ$m and inter-obstacle distance of 121 $μ$m are more appropriate. These mixers enabled 80{%} mixing efficiency creating a pressure drop of 6.0 Pa at Re = 0.1 and 5.1 × 104 Pa at Re = 117.6, with a mixer length of 2.5 mm. To the authors' knowledge, the developed mixer is one of the shortest planar passive micromixers reported to date.