Spray coating of self-aligning passivation layer for metal grid lines

In applications such as organic light emitting diodes (OLEDs) or photovoltaic cells a homogenous voltage distribution in the large anode layer needs to be ensured by including a metal grid with a transparent conductor layer. To ensure sufficient conductivity, relatively thick metal lines are used, which increases the risk of electrical shorts between the anode and the cathode. For this reason an insulating layer is needed on top of the metal lines. The thick metal lines limit the choice of deposition method, since some methods such as spin coating require smooth surfaces and cannot be used for applying the insulator. Here, a spray coating process has been studied as a potential alternative deposition method to create thin resistive layers on rough surfaces. Spray coating and Joule heating has been used for the alignment of insulator films on printed metal lines. It was demonstrated that spray coating can be used to cover the printed metal lines which have high peaks on them. The spray coating forms electrically insulating layers even though the film thickness is less than the height of the peaks. The leakage current through the dielectric was on the order of 10^-6 A/cm².