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Geetha Bolla, Speaker at Materials Congress
Bengurion University, Israel
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.



Geetha Bolla is currently a postdoc fellow at Ben-Gurion University, Israel. She was awarded a Ph.D. degree from University of Hyderabad in 2015. She has worked as research fellow ICCAS Beijing (2016−2017), an INDO-US Fellow at Massachusetts Institute of Technology (2017−2018), and at the National University of Singapore (2018-2020). Her research interests are on the design, crystallization, and bioavailability of pharmaceutical cocrystals, organic semiconductors and optoelectronics, heterogeneous nucleation, and smart photo- and thermo-salient materials. The main driving motivation in her research is solid-state chemistry and crystallization mechanisms, and their function in smart bioinspired materials and healthcare products.