DACT-II exhibits a near zero ΔEST of 0.009 eV yet a large oscillator strength, f, reflected in the unity FPL (9 wt% in CBP film). These desirable traits translate into a green OLED that shows an impressive EQEmax of 29.6% with λEL at ~520 nm. The high efficiency of the device is also due to the preferential horizontal orientation of the TDM of DACT-II as determined by VASE measurements (S = -0.32) in Figure and angular-dependent PL measurements (S = -0.29) in Figure . Kim et al. later showed that efficiency roll-off can be suppressed in the OLED if the CBP host is replaced by a TCTA:B3YPMPM exciplex-forming host, as the authors found a 1.5-fold increased RISC rate in this system (krisc: CBP 1.37´10 5 s -1 ;