An electronic device, such as, without limitation, a perovskite solar cell or a light emitting diode, includes an assembly including at least one electronic portion or component, and a composite coating layer covering at least part of the assembly including the at least one electronic portion or component. The composite coating layer includes a polymer material, such as, without limitation, PMMA or PMMA-PU, having nanoparticles, such as, without limitation, reduced graphene oxide or SiO2, embedded therein. The electronic device may further include a second coating layer including a second polymer material (such as, without limitation, PMMA or PMMA-PU without nanoparticles) positioned between the coating layer and the assembly.