Anti-Kasha Triplet Energy Transfer: Excitation Wavelength Dependent Persistent Luminescence from Host-Guest Doping Systems

Abstract

Anti-Kasha’s emission in organic luminogens has attracted many attentions since its discovery. However, only limited examples of anti-Kasha rule have been reported and anti-Kasha triplet energy transfer (ET) is even less-touched. This work provided an efficient strategy to realize excitation wavelength dependent (Ex-De) afterglow in a host-guest system benefiting from anti-Kasha rule. Host has almost imperceptible RTP upon 365 nm excitation and guest is totally RTP inactive, while the doping system exhibits Ex-De afterglow with improved quantum yields. Anti-Kasha triplet ET process is demonstrated from the higher excited triplet state T2 of host to the lowest excited singlet state S1 of the aggregated/unimolecular state of guest. ET efficiency in the doping system could be tuned by adopting denser or looser intermolecular packing through simply changing processing methods. The strategy of anti-Kasha triplet ET endows doping system with multiple stimuli-responsive properties, including Ex-De afterglow, mechano- and thermal-triggered afterglow behavior. Corresponding applications are also realized in multiple information anti-counterfeiting and display.