An electronic device and methods for its preparation comprising an active area between first and second conductive layers on a substrate; the active area is in a well whose bottom is a patterned first conductive layer on the substrate, the sides of the well are bank structures comprising a non- radiative active fluoropolymer which overlap the edges of the first conductive layer and which are in contact with the substrate. The well contains active materials, preferably introduced by a solution method such as ink-jet. The second conductive layer is located over the top of the well.