Luminance Enhancement Mechanisms for Blue Organic Light-Emitting Devices Utilizing a Double Emitting Layer

Abstract

Blue organic light-emitting devices (OLEDs) were fabricated utilizing fluorescent materials of 2-methyl-9,10-bis(naphthalene-2-yl)anthracene (MADN), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthorlene (BCP), and 1,3-bis(carbazol-9-yl)benzene (mCP). The emitting layer (EML) of the blue OLEDs consisting of a hole buffer layer and a blue fluorescent layer provided the efficient formation of the electron-hole pairs. The maximum luminance of the OLEDs with a BCP-doped MADN/MADN-doped mCP double EML at 10 V was 10,270 cd/m(2), which was much larger than that of blue OLEDs with a single EML. The holes injected from the indium-tin-oxide anode were accumulated at the BCP-doped MADN/MADN-doped mCP and the MADN-doped mCP/BCP heterointerfaces, resulting in the generation of the Coulomb force. The maximum luminance of the blue OLEDs with a double EML significantly increased due to an increase in the recombination rate of the electrons and holes resulting from the existence of the hole-induced Coulomb force. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3615977] All rights reserved.