X-shaped tetra-substituted pyrenes: Synthesis, photophysics, and electroluminescence

Two X-shaped compounds (7 and 9) based on pyrene have been synthesized and well characterized. These compounds exhibit good thermal stabilities and high fluorescence yields. In addition, an interesting phenomenon is discovered that the fluorescence of compound 9 can be reversibly converted from red to orange in the solid state. Organic light-emitting diodes have been fabricated using the X-shaped compounds as the host emitter with low turn-on voltage up to 2.35 V. The device based on compound 7 exhibits orange-red electroluminescence (CIE: 0.58, 0.42) with a maximum luminance of 4798.4 cd/m2, a maximum current efficiency 1.26 cd/A, and a power efficiency of 1.06 l m/W.