Influence of polymer matrix in the luminous efficiency of organic light-emitting electrochemical cells

In this work, the polymer was incorporated into the luminescent materials to form many encapsulated domains that could possible limit the forming of positive and negative charged layer inside each domain. This was expected to increase the luminescent area and hence the efficiency. Several polymers were used, including Poly(4-vinylphenol) (PVP), Poly (vinyl alcohol) (PVA), Poly (methyl methacrylate) (PMMA), Poly (ethylene Oxide) (PEO) and Poly(3,4- ethylenedioxythiophene) (PEDOT). To understand the effect of these polymers to the efficiency. The OLEC devices with Ru(bpy)₃(PF₆)₂, red-emitting materials, were made. Red light emitting was found in the OLEC devices with PVA, PMMA, and PEO polymer matrix. The highest efficacy of approximately 0.3 lm/W was obtained in the Ru (bpy)₃ OLEC with PEO as matrix, which is almost 100 times higher than the device with PVA as matrix. The reason of high luminescent efficiency was primary attributed to the low injection barrier for carrier from PEO into encapsulated Ru(bpy)₃(PF₆)₂. The result of this work indicates the forming of micro-encapsulated domain in the OLEC could enhance the luminous and the efficacy effectively.