A direct observation of up-converted room-temperature phosphorescence in an anti-Kasha dopant-matrix system.

Abstract in brief

• The study reports a surprising discovery of upconverted room-temperature phosphorescence (RTP) with a lifetime of about 0.1 seconds in a system where a dopant (BPBF) is embedded in phenyl benzoate matrices, challenging the usual understanding that phosphorescence emissions have longer wavelengths than fluorescence.
• The upconverted RTP originates from the Tn2 states of BPBF, which have n-character from benzophenone parts, and these states form a T-to-T equilibrium after intersystem crossing, enabling rapid phosphorescence that can directly emit RTP, thus illustrating a violation of Kasha's rule.
• This finding enhances our understanding of triplet excited state dynamics and could lead to new types of materials like deep-blue afterglow emitters and stimuli-responsive afterglow compounds that are excitable by visible light.]