Excitation-Dependent Triplet–Singlet Intensity from Organic Host–Guest Materials: Tunable Color, White-Light Emission, and Room-Temperature Phosphorescence

A series
of organic host–guest materials with multifunctional
luminescence were constructed. Four isoquinoline derivatives were
used as the guests, and benzophenone was used as the host. The doped
system exhibited excellent dual emission with cyan fluorescence and
orange-yellow room-temperature phosphorescence, and the dual emission
could be combined into almost pure white-light emission. Importantly,
the relative intensity of the fluorescence–phosphorescence
could be adjusted by changing the excitation wavelength, with the
phosphorescence intensity being significantly higher than the fluorescence
intensity under shorter excitation wavelengths and vice versa under
longer excitation wavelengths. Therefore, three-color emission switching
among cyan, white, and orange could be achieved by simply adjusting
the excitation wavelength. The results of experimental and theoretical
calculations indicated that the excitation-dependent emission colors
were caused by different transfer paths for excitons under different
excitation wavelengths. These materials with multifunctional luminescence
could be used as writable inks for advanced anticounterfeiting.