Large room-temperature magnetic field effect of photoluminescence in few-layer metal-free semiconductor fluorographene

Organic semiconducting materials with large magnetic field effect on photoluminescence (MFEPL) is expected to be superior in innovative opto-spintronics. However, the magnitude of positive MFEPL has remained relatively weak. While fluorinated graphene may give the favorable conditions for elevating the MFEPL performance triggered by smaller spin-exchange interaction within intermolecular charge-transfer (CT) states, and their MFEPL has not been investigated. Here, we report a substantial positive MFEPL, featuring a magnitude of 32.5% at room temperature, in few-layer fluorographene (FG) dispersed in hexanol under an applied magnetic field of 840 mT. Remarkably, the MFEPL remains available at 17.65% when the field is reduced to 176 mT. Additionally, a large positive MFEPL of 14.36% is observed in FG:BCP composite film. We demonstrate that MFEPL can be effectively tuned by controlling the FG layer number and the dielectric constant of the organic solvent used for dispersion. These findings reveal that the intermolecular charge-transfer (CT) states in donor-acceptor composites are contributors to the improved MFEPL.