Electro-optical properties of poly(1-(difluorophenyl)-2-(4-alkylcyclohexyl phenyl)acetylene) organic light-emitting diodes

Abstract

For organic light-emitting diodes (OLEDs) applications, we have investigated novel polymers, using substituted polyacetylenes (PA), poly(1-(fluorophenyl)-2-(alkylcyclohexylphenyl)acetylene) (PDPA-nF) ( n = 1 or n = 2) which exhibit air stability, better solubility in common organic solvent and higher luminescence than polyacetylene. In this study, we have used poly[(1-(3,4-difluorophenyl)-2-(4-pentylcyclohexylphenyl)acetylene)] (PDPA-2F) as an emitter in OLEDs and their performance was determined by measuring the current–voltage–luminance characteristic. The devices have a maximum brightness of 827 candela (cd)/m 2 at 12 V and a maximum current efficiency of 0.78 cd/A at 9 V with a maximum luminescence at 536 nm. Influence of the metal electrode on the charge injection was studied using several cathode configurations (Ca, Al and Au) for the devices. Furthermore, the charge injection and transport processes were correlated to the presence of traps inside the polymer, determined by deep level transient spectroscopy (DLTS).