HAPPY Dyes as Light Amplification Media in Thin Films

A series
of 1H amorphous tri-phenyl pyridine (HAPPY) dyes have been
synthesized from luminescent triphenyl-group-containing 2-methyl-6-styryl-substituted-4H-pyran-4-ylidene derivatives in reactions with benzylamine
and investigated for suitability as solution-processable light-emitting
medium components in thin films for amplified spontaneous emission
(ASE). Conversion of a 4H-pyrane ring into a 1H-pyridine fragment enables aggregation-induced emission
enhancement (AIEE) behavior in the target products and slightly increases
thermal stability, glass transition temperatures, and ASE efficiency
with PLQY up to 15% and ASE thresholds as low as 46 μJ/cm2 in neat spin-cast films, although thermal and photophysical
properties are mostly dominated by the incorporated electron acceptors.
Continued lasing parameter efficiency parameter improvement experiments
revealed that no further optimization of HAPPY dyes by doping in polymer
matrixes is required as the amplified spontaneous emission thresholds
were lowest in pure neat films due to the AIEE phenomenon.