Pyrene-capped starburst emitters as gain media for organic lasers: Design, synthesis, and stabilized lasing properties

A set of pyrene-capped starburst organic emitters composed of a non-planar cross-shaped spirofluorene core (SF-PyF) and a large rigid planar pyrene core (Py-PyF) have been designed, synthesized and explored as efficient emitters for organic lasers. High photoluminescence yields and excellent thermal stability of SF-PyF and Py-PyF in neat films make them promising optical gain media. Low amplified spontaneous emission (ASE) thresholds of 6.6 μJ cm^-2 (1.3 kW cm^-2) at 451 nm for SF-PyF and 5.4 μJ cm^-2 (1.1 kW cm^-2) at 490 nm for Py-PyF were obtained (pump pulse: λ_p = 355 nm, 10 Hz, 5 ns). Distributed feedback (DFB) lasers based on SF-PyF and Py-PyF exhibited good performance with low thresholds (16 nJ per pulse for SF-PyF and 24 nJ per pulse for Py-PyF, respectively) and the full width at half maximum of about 0.2 nm. Surprisingly, DFB lasers integrated with SF-PyF and Py-PyF as gain media exhibited excellent ambient photostability and superior reliability even in hot water (80 °C). The excellent stability of ASE spectra, electroluminescence spectra and lasing spectra under harsh conditions manifests that the resulting pyrene-capped starburst emitters are beneficial for improving the lasing stability issues. The study sheds light on exploring robust organic gain media toward electrically pumped OSLs.