Room-temperature multiple phosphorescence from functionalized corannulenes: temperature sensing and afterglow organic light-emitting diode

Corannulene-derived materials have been extensively explored in energy storage and solar cells, but, however, are rarely documented as emitters in light-emitting sensors and organic light-emitting diodes (OLEDs), due to low exciton utilization. Here, we report a family of multi-donor and acceptor (multi-D-A) motifs, TCzPhCor, TDMACPhCor, and TPXZPhCor, using corannulene as the acceptor and carbazole (Cz), 9,10-dihydro-9,10-dimethylacridine (DMAC), and phenoxazine (PXZ) as the donor, respectively. By decorating corannulene with different donors, multiple phosphorescence is realized. Theoretical and photophysical investigations reveal that TCzPhCor shows room-temperature phosphorescence (RTP) from the lowest-lying T₁; however, for TDMACPhCor, dual RTP originating from a higher-lying T₁ (T₁^H) and a lower-lying T₁ (T₁^L) can be observed, while for TPXZPhCor, T₁^H-dominated RTP occurs resulting from a stabilized high-energy T₁ geometry. Benefiting from the high-temperature sensitivity of TPXZPhCor, high color-resolution temperature sensing is achieved. Besides, due to degenerate S₁ and T₁^H states of TPXZPhCor, the first corannulene-based solution-processed afterglow organic light-emitting diodes (OLEDs) is investigated. The afterglow OLED with TPXZPhCor shows a maximum external quantum efficiency (EQE_max) and a luminance (L_max) of 3.3% and 5167 cd m^-2, respectively, which is one of the most efficient afterglow RTP OLEDs reported to date.