Solution processable carbazole derivatives for dopant free single molecule white electroluminescence by room temperature phosphorescence

Abstract

White electroluminescence from a single molecule is a challenging topic in organic light emitting diode (OLED) research. Herein, we report the white light emission from a carbazole derivative, 9-ethyl-3,6-bis(4-(trifluoromethyl)phenyl)-carbazole (Cz(PhCF3)2), by harvesting both singlet and triplet emissions. The blue fluorescence and a broad emission from room temperature phosphorescence resulted in white light electroluminescence (EL) with a colour coordinate of (0.31, 0.44). We successfully synthesized another molecule namely 1,1'-(4,4'-(9-ethyl-9H-carbazole-3,6-diyl)bis(4,1-phenylene))diethanone Cz(PhBz)2 and achieved a four-fold increase in the efficiency of the EL with a substitution change from −Ph-CF3 to −Ph-CO-Ph with a colour coordinate of (0.29.0.35). The present route for the generation of white light emission from a solution processable single organic molecule utilizing both singlet and triplet excitons offers a promising way to improve the efficiency of future white OLEDs.