Low Amplified Spontaneous Emission Threshold from Organic Dyes Based on Bis‐stilbene. (20th June 2018)

• Record Type: Journal Article
• Authors: Mamada, Masashi; Fukunaga, Toshiya; Bencheikh, Fatima; Sandanayaka, Atula S. D.; Adachi, Chihaya
• Is Part Of: Advanced functional materials. Volume 28:Number 32(2018)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2018-06-20
• Subjects: amplified spontaneous emission (ASE) -- bis‐stilbene -- organic laser dyes -- organic light‐emitting diodes (OLEDs) -- organic semiconductors; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.201802130
• Languages: English
• ISSNs: 1616-301X

Abstract

Abstract: 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 µJ 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 µJ 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. Abstract : Low amplified spontaneous emission thresholds below 1 µJ cm −2 are achieved in a series of bis‐stilbene with carbazole derivatives and are attributed to high photoluminescence quantum yields (≈100%), large radiative decay rates (10 −8 –10 −9 s −1 ), and low excited state absorption cross sections. In addition, the new organic laser dyes have high solubility and/or bipolar properties.