Electrochemiluminescent and electroluminescent devices containing polypyridine transition metal complexes

Light emitting devices based on solid thin layers of organic compounds and/or inorganic coordination complex materials fall into two general categories, electrochemiluminescent (ECL) and electroluminescent (EL) systems. The basic description of the two device motifs is quite similar; however, there are a number of critical differences in the mechanisms by which they operate. These considerations in turn dictate the choices of materials employed in the construction of the two types of devices. The introductory chapter in this work describes in detail the conceptual differences between ECL and EL devices, and the resulting materials requirements.; In the second chapter, an ECL system is described based on a substituted tris(bipyridine)ruthenium (II), “[Ru(LL)₃]”, monomer complex which exhibits intense emission following either photo- or electrochemically-generated excitation. A solid state “sandwich cell” device is constructed following thermal polymerization of the complex and the performance of this device is reported.; In the third chapter, a series of three polymerizable [Ru(LL)₃]-based complexes is examined. The electronic properties of films composed of these materials are studied after careful electrochemical reduction to yield conductive polymers, with emphasis on conductivities and work functions. These materials are considered for use as the cathode layers for EL devices employing commonly reported emissive compounds. The reduced [Ru(LL)₃] conducting polymer with the lowest work function was successfully used as a cathode in devices with two common EL materials. These results sufficed as proof-of-concept for the use of reduced coordination complexes as cathodes in EL devices, but their performance was less than ideal.; Finally, the fourth chapter describes a related set of three coordination complexes of ruthenium and chromium (discrete molecules rather than polymers) that are also electrochemically reduced and subsequently used as cathode materials for EL devices. However, these complexes can be vapor deposited in the conductive state, and thus have important advantages in actual devices. The performance of systems including layers of these vapor deposited complexes is evaluated and is significantly improved over those devices reported in the previous chapter.