The emission of DDiKTa-A shows a significant temperature sensitivity in 2-MeTHF, reflected in a color change from 566 to 638 nm across a temperature range from 123 to 298 K. In 2 wt% doped films in 1,3-bis(N-carbazolyl)benzene (mCP), DDiKTa-A emits at 562 nm, has a high photoluminescence quantum yield, FPL, of 92%, and a delayed lifetime, td, of 279 µs. The OLEDs with DDiKTa-A showed an EQEmax of 20.3% at lEL of 573 nm but with a severe efficiency rolloff (EQE100 of 13.2%). To tackle the observed efficiency roll-off, hyperfluorescence (HF) devices incorporating 4CzIPN as the assistant dopant were fabricated and showed much improved performance, with an enhanced EQEmax of 24.3% and a reduced efficiency roll-off with EQE100 of 22.5% and EQE1000 of 14.6% at lEL of 574 nm.