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.
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