Diffusion – the Hidden Menace in Organic Optoelectronic Devices

In a film stack of bathocuproine (BCP) (electron transport layer), fac -tris(2-phenylpyridyl)iridium(III) [Ir(ppy)3] blended in 4,4′-bis(N -carbazolyl)biphenyl (CBP) (light-emitting layer), and 4,4′,4″-tris(N -carbazolyl)triphenylamine (TCTA) (hole transport layer), the BCP and Ir(ppy)3:CBP layers rapidly interdiffuse by anomalous Fickian diffusion. Diffusion leads to a decrease of up to 33% in the solid-state emission but no change in color.