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

Organic semiconducting materials with a large magnetic field effect on photoluminescence (MFE_PL) are expected to be superior in innovative opto-spintronics. However, the magnitude of positive MFE_PL has remained relatively weak. While fluorinated graphene may give the favorable conditions for elevating the MFE_PL performance triggered by smaller spin-exchange interaction within intermolecular charge-transfer (CT) states, and it's MFE_PL has not been investigated. Here, we report a substantial positive MFE_PL, 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 MFE_PL remains available at 17.65% when the field is reduced to 176 mT. Additionally, a large positive MFE_PL of 14.36% is observed in the FG:BCP composite film. We demonstrate that MFE_PL 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 MFE_PL.