Deep-Red Amplified Spontaneous Emission from cis-Configured Squaraine

We report deep-red amplified spontaneous emission (ASE) from cis -configured squaraine ( cis -DCSQ1) under optical pumping. Doping of cis -DCSQ1 into a 4,4′-bis(9-carbazolyl)-2,2′-biphenyl (CBP) host film at an appropriate concentration (0.5 wt % for this system) led to a marked increase of photoluminescence quantum yield because of efficient CBP-to- cis -DCSQ1 Förster resonance energy transfer and suppression of aggregation-caused quenching. Thus, this doped film showed clear ASE with a threshold of around 10 μJ cm –2 and peak wavelength of 687 nm. These results proved that cis -configured squaraine derivatives are promising as gain materials for future applications as deep-red organic lasers.