Short-range charge transfer for efficient ultra-narrowband deep blue afterglow.

Efficient and narrowband blue organic afterglow materials are critical components for advanced optoelectronic applications, but so far, have been rarely explored. Herein, we report short-range charge transfer-assisted high efficiency and ultra-narrowband deep blue (<450 nm) afterglow from a series of indolocarbazole-based chromophores. The short-range charge transfer within the fused π-conjugated frameworks enlarges the singlet-triplet energy gap and suppresses vibronic coupling and structural relaxations, thus leading to a slow reverse intersystem crossing rate, a long delayed-fluorescence lifetime of up to 186.48 ms and a high photoluminescence quantum yield of 86.1%. Notably, these afterglow emitters exhibit ultra-narrow full width at half maximum of 18 nm, presenting high colour purity with y colour coordinates below 0.05. Taking advantage of these unique afterglow features, the potential for encrypted light communications and high-resolution afterglow displays are demonstrated. This work not only provides an effective strategy for developing narrowband organic afterglow materials but also extends their applications to advanced fields.