Low Amplified Spontaneous Emission Threshold from Organic Dyes Based on Bis-stilbene

Advanced organic laser dyes exhibiting high solubility and bipolar behavior are developed based on a structure combining bis-stilbene with carbazole (BSBCz). The materials show high photoluminescence quantum yields and large radiative rate constants in solutions, crystals, and blend and neat films. The introduction of alkyl groups significantly improves the solubility of BSBCz, and solution-processed films of the alkyl-substituted derivatives exhibit amplified spontaneous emission thresholds as low as 0.59 mu J cm(-2), which is comparable to those of vacuum-deposited BSBCz films. On the other hand, cyano-substitution on BSBCz (BSBCz-CN) increases electron-accepting properties, resulting in a bathochromic shift of the emission wavelength and improved bipolar behavior. In a BSBCz-CN-doped film, a low ASE threshold of 0.63 mu J cm(-2) is achieved, which is one of the lowest values for organic laser dyes with green emission. In addition, organic light-emitting diodes based on BSBCz-CN neat films exhibit external quantum efficiencies of 1.8% and could withstand injection of high current densities of up to 500 A cm(-2) under pulse operation. These properties along with low excited-state absorption cross sections make these materials an outstanding addition to the existing library of organic laser dyes, especially for consideration in electrically pumped lasers.