Title : Halogen bond Cocrystals: Tailoring Multiple Radiative Decay Pathways for Amplified Spontaneous Emission
Halogen-bonded cocrystallization of anthracene derivative discussed towards Amplified spontaneous emission (ASE) which is intrinsically associated with lasing applications. Based on our results, we have defined some important guidelines for cocrystallization of organic ASE materials, cocrystals DPYA-BrFB and DPYA-IFB with varied optical features by subtly tailoring halogen bonds from C–Br···N to C–I···N. Noticeably, stronger halogen bond and other short intermolecular contacts in the segregated-stack DPYA-IFB cocrystal account for a lower number of vibration modes with smaller Huang–Rhys factors, thus enhancing remarkably the radiative decay rate up to 4.3×10-2 ns−1 at the ASE band, which is 11.0 times as high as DPYA-BrFB. Due to the higher radiative decay rate, larger radiative decay selectivity together with the lower optical loss coefficient, the DPYA-IFB cocrystal even with PLQY as low as 3.0% features an improved ASE threshold of 22 μJ/c 2, which is 4.7 and 10.1 times as low as those of DPYA and DPYA-BrFB respectively without shifting the wavelength of ASE band significantly. Therefore, the tailor made packing structures and intermolecular interactions of organic chromophores by cocrystallization pave a promsing way to the development of organic ASE or lasing materials by delicately regulating the multiple radiative decay pathways.