HIGH-EFFICIENCY SILOLE-BASED MOLECULAR ORGANIC LIGHT-EMITTING DEVICES USING HIGHLY CONDUCTING POLYMER ANODE CONTACTS

摘要

We present high efficiency and high luminance molecular organic light-emitting diodes (MOLEDs) using a conducting polymer as a hole-injecting electrode (anode), a CsF/Al bilayer as a cathode, and silole derivatives as an emitter and/or an electron transporter. The conducting polymer films, poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS), were either spin-cast from aqueous dispersions or pre-coated on plastic substrates (courtesy of Agfa Gevaert N. V. Belgium). The surface sheet resistance of the conducting polymer films is in the range of 150 Ohms/sq ～1500 Ohms/sq. MOLEDs fabricated with a low sheet resistance (150 Ohms/sq) conducting polymer as an anode without using an ITO underlayer and CsF/Al as a cathode exhibit very low operating voltages (4.5V @ 100 cd/m~2 and 6.5V @ 1,000 cd/m~2). This good device performance is attributable to the low sheet resistance of the conducting polymer anode and the high electron mobility of the silole derivative, namely 2,5-bis-(2', 2"-bipyridin-6-yl)-1, 1-dimethyl-3, 4-diphenylsilacyclopentadiene (PyPySPyPy), used as an electron transporter. Efficient electron injection from the CsF/Al cathode to the PyPySPyPy electron injection/transport layer also contributes to better charge balance and improved device efficiency.