Fig. 2: Illustration of the interface exciplex formation.
From: High efficiency blue organic light-emitting diodes with below-bandgap electroluminescence

a Room temperature (RT) normalized PL spectra of TSPO1 and DBFPO pristine films and mixtures. b The PL spectra of mixtures taken at RT in nitrogen. c Temperature-dependent PL spectra of TSPO1:DBFPO 1:1 mixed film. d The chemical structures and frontier orbitals of DBFPO and TSPO1, and the illustration of interfacial exciplex formation.