The Host-Guest Interaction Effect in all Organic Room Temperature Phosphorescence Light-Emitting Electrochemical Cells

A series of metal-free dyes, rooted in bromofluorene (BrFX) were synthesized to harness phosphorescence at room temperature within amorphous films and light-emitting devices (LECs). By incorporating aliphatic and aromatic side groups onto the bromofluorene structure, we achieved substantial control over the resulting color and fine-tuned the intensity of the room temperature phosphorescence (RTP). Our selection of host materials, including 3,3’-di(9H-carbazol-9-yl)-1,1’-biphenyl and poly(9-vinyl carbazole) was guided by their energy bandgap and their ability to facilitate energy transfer to BrFX, with the aim of achieving high electrophosphorescence in BrFX, with the aim of achieving high electrophosphorescence in BrFX based LECs. The intensity of the electrophosphorescence was strongly reliant on the chosen host. In-depth investigations employing theoretical computations based on density functional theory, infrared studies, and single crystal X-ray diffraction unveiled the crucial nature of the interaction between the host’s ring structure and the guest material in influencing electrophosphorescence. This study sheds light on the impact of host-guest interactions and the role of energy transfer within the host material in endabling room temperature phosphorescence in a device.