Consequently, most reported RTP research has focused on enhancing RTP efficiency (i.e., photoluminescence quantum yield, F PL ) and t ph . To date, there are only a few documented examples where RTP originates from a higher-lying triplet excited state. For instance, Tang and co-workers reported several benzothiophene derivatives showing dual phosphorescence, which was assumed to originate from both the first (T 1 ) and second (T 2 ) triplet excited states (Figure ). Huang and co-workers designed materials based on carbazole that enabled dual phosphorescence from T 1 and an H-aggregation stabilized species (T 1 * , T 1 * < T 1 ) (Figure ). However, this dual phosphorescence was only observed to occur in crystals, making it difficult to identify the implication of any higher-lying triplet states in the emission processes. Recently, Zhang and co-workers developed a series of triphenylamine-sp 3 linker-acceptor motifs exhibiting phosphorescence that was attributed to a high-lying T 1 (T 1 H ) state associated with the electronically decoupled donor and acceptor groups in the compound (Figure ). Nevertheless, emission from the T 1 H state could only be observed at low temperature (< 250 K). It thus remains a formidable challenge to design RTP materials whose emission originates from higher-lying triplet excited states.