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The influence of ZnO seed layer thickness in Squaraine (SQ) is investigated: PC71BM bulk heterojunction solar cells that incorporate ZnO nanorods. The thickness of the ZnO seed layer varies between 16–249 nm by changing the concentration of the precursor solution. With atomic force microscopy (AFM), X‐Ray Diffraction (XRD), and Scanning Electron Microscopy (SEM) studies, it is shown that this approach allows to systematically tune the thickness of the ZnO seed layer without influencing seed layer grain size, or the morphology of the ZnO nanorods that are deposited on top of the seed layer. The proof‐of‐concept is demonstrated in SQ:PC71BM solar cells. It is found that seed layers with 55 nm thickness yield the highest short circuit current densities, resulting in power conversion efficiencies of 2.5 ± 0.1%. These results are compared to SQ:PC71BM solar cells prepared in planar architectures, and it is observed that both device architectures yield comparable results. The optimized nanostructured ZnO electrode enables the fabrication of BHJ devices with thick active layers without the loss in solar cell performance.

In2S3(1–x)O3x is known from preceding studies to have a bandgap varying continuously as a function of x, which is the reason why this solid solution is potentially interesting in the field of photovoltaics. In this work, we present results on oxidation of In2S3 by heating in air atmosphere to obtain the desired material. The oxidation is accompanied by a mass loss due to the substitution of S by O atoms that is studied by means of thermogravimetric analysis. It appears that the temperature region in which the oxidation occurs is strongly dependent on the microstructure of deposited films. As‐grown films deposited by chemical bath deposition are subjected to nano‐oxidation occurring at lower temperature than oxidation of materials that are characterized by a better crystallinity and larger crystallite size. X‐ray diffraction and scanning electron microscopy (including energy dispersive X‐ray spectroscopy (EDX)) were used to get information on the compounds and the microstructure of films. The main conclusion of the paper opens the perspective of practical applications for producing layers for solar cells.

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