Chemical solution deposition techniques are a very competitive low cost method to achieve coated conductors. Recently, fluorine-free CSD methods have made a great progress for the preparation of YBCO thin films and became a sustainable alternative for the well-known trifluoroacetate CSD approach. By elucidating the reaction mechanism behind this new approach, finally giving an answer to the question why it is possible to fabricate YBCO films without TFA, different processing routes were discovered giving rise to high superconducting YBCO films (>1MA.cm-2). Each route has it's own benefits. One specific route offers the opportunity to tune the crystallographic orientation. By changing one process parameter, a shift from complete c-axis to complete a-axis orientation is observed. This can be very useful for e.g. Josephson Junctions.
We particularly investigated the fundamental reaction mechanism of each reaction route, with the focus on the corresponding barium compound. Although good superconducting properties are obtained, still one major drawback limits industrial implementation: thickness. It is observed that a critical thickness of ∼500 nm eliminates the superconducting properties. Therefore, this paper gives a summary of all progress made regarding to fluorine-free water-based CSD YBCO thin films with emphasis on the possibility to control the crystallization rate.