No abstract

Experimental evidence for reverse intersystem crossing (RISC) in organic light‐emitting devices with small energy gaps between the singlet and triplet excited states is given using the magnetic field effect (MFE) on the electroluminescence (EL) of the devices. The EL decreases when an external magnetic field is applied, indicating that the RISC process occurs and promotes the exciton in the device. The MFE could be a good tool for exploring physical processes in organic semiconductors, especially when spin effects are involved.

The >10,000 living venomous marine snail species [superfamily Conoidea (Fleming, 1822)] include cone snails (Conus), the overwhelming focus of research. Hastula hectica (Linnaeus, 1758), a venomous snail in the family Terebridae (Mörch, 1852) was comprehensively investigated. The Terebridae comprise a major monophyletic group within Conoidea. H. hectica has a striking radular tooth to inject venom that looks like a perforated spear; in Conus, the tooth looks like a hypodermic needle. H. hectica venom contains a large complement of small disulfide-rich peptides, but with no apparent overlap with Conus in gene superfamilies expressed. Although Conus peptide toxins are densely post-translationally modified, no post-translationally modified amino acids were found in any Hastula venom peptide. The results suggest that different major lineages of venomous molluscs have strikingly divergent toxinological and venom-delivery strategies.

Using the magneto-electroluminescence (MEL) as a tool, we demonstrated the efficient inter-conversion between singlet and triplet charge-transfer (CT) states in exciplex-based organic light-emitting diodes (OLEDs). Results show that the MEL of exciplex-based device is larger than that of exciton-based device by a factor of 3.2. The emission of exciplex-based devices comes from the direct intermolecular electron-hole pair recombination and their spin exchange energy is much smaller, which causes the efficient inter-conversion between singlet and triplet states. This argument was supported by the consistent evolutions of the MEL and EL spectra versus applied bias and donor concentrations. Finally, the bandgap effects on the MEL as well as the external quantum efficiency of exciplex-based devices were discussed. Our findings of MEL may offer a feasible way to unravel underlying mechanisms that limit the EL efficiency in the OLEDs.

The singlet–triplet inter-conversion in CT fluorescent materials is a dynamic process, and the deactivation rates of singlet and triplet determine the direction of the conversion.