Propagation dynamics of a spatiotemporal vortex pulse in the spatial fractional system

The dynamics of wave packets carrying a spatiotemporal vortex in the spatial fractional system is still an open problem.The difficulty stems from the fact that the fractional Laplacian derivative is essentially a nonlocal operator,and the vortex is space-time coupled.Here,we investigate the transmission of spatiotemporal vortices in the spatial fractional wave equation(FWE)and demonstrate the effects of linewidth,vortex topological charge,and linear chirp modulation on the transmission of Bessel-type spatiotemporal vortex pulses(BSTVPs).Under narrowband conditions,we find that the propagation of BSTVP in the FWE can be seen as the coherent superposition of two linearly shifted half-BSTVPs and can reveal orbital angular momentum backflow for the half-BSTVP.Our analysis can be extended to other spatiotemporal vortex pulses.

Toward Eco-friendly Green Organic Semiconductors： Recent Advances in Spiro[fluorene-9,9＇-xanthene] （SFX）-Based Optoelectronic Materials and Devices

Green organic semiconductors （GOS） have the four-element features, including biomass as stuffs, synthesis with the pot, atom and step economic （PASE） route, eco-friendly fabrication processes in aqueous phase, and recy- clable devices, capturing the trend of organic electronics in the future. Herein, we reviewed the efforts that have been made on GOS by our group. We first made a brief introduction of organic （opto）electronics, followed by the design strategies of GOSs based on spirofluorenes. Concretely, we described the discovery of one-pot protocol to spirofluorenres and a pot-atom-step economic （PASE） platform of spiro[fluorene-9,9＇-xanthene] （SFX） for the mo- lecular design of organic semiconductors, as well as a state-of-the-art nanocrystalline films with eco-friendly pro- cedures. Then, we highlighted the progress on SFX-based organic semiconductors in the organic light-emitting di- ode （OLED） field. Finally, we conducted a summary on SFXs in OLED and an outlook on green semiconductors starting from biomass, via one-pot to spirofluorenes, to water-phase devices.

Carbazole-endcapped Spiro[fluorene-9,9＇-xanthene] with Large Steric Hindrance as Hole-transporting Host for Heavily-doped and High Performance OLEDs

In this work, we designed and synthesized a novel spirocyclic compound functionalized spiro[fluorene-9,9＇- xanthene] with carbazole group （2-carbazolyl-spiro[fluorene-9,9＇-xanthene], SFX-Cz） via Friedel-Crafts and Ullmann reaction, which is expected to own high thermal and morphological stability, and good carrier injection/ transporting properties due to the excellent hole transporting characteristics of carbazole and cruciform structure of spiro[fluorene-9,9＇-xanthene]. The carbazole end-capped spiro[fluorene-9,9＇-xanthene] SFX-Cz based PhOLEDs with Flrpic as phosphor emitter have been researched by varying dopant concentration, which exhibit the maximum EQEs of 8.9%, 7.4%, 9.1%, and 4.7% with the doping increasing from 10% to 50%. The higher performance PhOLEDs are independent on concentration variation from 10% to 30%, which suggests the bulky steric hindrance of SFX-Cz might be a potential canditate for high performance and inexpensive device with simplified process.