Effects of Al, Ag, and Ca on luminescence of organic materials

Organic materials have been demonstrated to have the necessary attributes for display applications. In typical organic light emitting devices, metallic electrodes are used to inject charged carriers into the organic electroluminescent (EL) medium. We report severe photoluminescence (PL) quenching of organic thin films comprising the most useful materials, namely 1,4-bis[4-(3,5-di-tert-butylstylyl)styryl]benzene (4PV), upon sub-monolayer deposition of Al, Ag, and Ca in an ultrahigh vacuum environment. The severity of the luminescence quenching, which depends on the type of metal used, can greatly affect the EL device performance. For example, a sub-monolayer coverage of the various metals on a 300 Angstrom 4PV thin film can reduce the PL by as much as 50%. Depositing the 4PV layer onto a metal substrate also exhibits PL quenching. An exciton diffusion length of 200 Angstrom can be estimated from the quenching data. (C) 1997 American Vacuum Society.