Anti-Kasha triplet energy transfer and excitation wavelength dependent persistent luminescence from host-guest doping systems

Abstract Anti-Kasha’s process in organic luminogens has attracted many attentions since its discovery. However, only limited examples of anti-Kasha’s rule have been reported and anti-Kasha triplet energy transfer (ET) is even less-touched. Benefiting from anti-Kasha’s rule, this work provided an efficient strategy to realize excitation wavelength dependent (Ex-De) afterglow in a host-guest system. The host has almost imperceptible RTP upon 365 nm excitation and guest is totally RTP inactive, while the doping host-guest system exhibits Ex-De afterglow with improved quantum yields. Anti-Kasha triplet ET process is realized from the higher excited triplet state T 2 of host to the lowest excited singlet state S 1 of the aggregated/unimolecular guest . ET efficiency in the doping system could be tuned by simply changing its processing methods to guide host and guest to adopt denser or looser intermolecular packing. The strategy of anti-Kasha triplet ET endows the host-guest doping system with multiple stimuli-responsive properties, including Ex-De afterglow, mechano-, and thermal-triggered afterglow behaviors. The corresponding applications of these properties are also realized in multiple information anti-counterfeiting and display.