Adachi et al. also performed a study to elucidate the importance of the bridging phenylene by comparing CzT (λPL: 502 nm; ΔEST: 0.09 eV; τd: 43 μs; ΦPL: 40%; 3 wt% in DPEPO) with BCzT (λPL: 483 nm; ∆EST: 0.3 eV; τd: 33 μs; FPL: 96%; 6 wt% in DPEPO) and demonstrated that the bridging phenylene contributes to increasing the overlap density between the electronic wave functions of the ground state and the lowest excited singlet state, leading to both a larger DEST and higher FPL, yet surprisingly a blue-shifted λPL. CzT, first reported in 2013 by Adachi et al., shows a small ∆EST of 0.09 eV. The reported OLED shows an EQEmax of only 6% due to the relatively low FPL of 40%. The S1 → S0 radiative decay of BCzT is significantly enhanced, leading to a much higher FPL of 96% (6 wt% in DPEPO), while the emission blue-shifted by The EQE of the OLEDs also depend on the orientation of the TDM of the emitters, which affects the light out-coupling efficiency of the device. Wang et al. prepared two TADF emitters IndCzpTr-1 (FPL: 75.2%, 10 wt% in mCBP) and IndCzpTr-2 (FPL: 71.9%, 20 wt% in mCBP) containing an indolocarbazole-based donor (Figure ). IndCzpTr-2 possesses a slightly smaller ΔEST of 0.11 eV than the 0.13 eV for IndCzpTr-1. The more extended structure of IndCzpTr-2 leads to a preferential horizontal orientation of the TDM in the neat film with an orientation order parameter, S, of -0.264 (estimated by VASE). The S value of IndCzpTr-1 in the neat film is only -0.1, which is far away from the theoretical value of S = -0.5 for a perfectly horizontal orientation of the TDM. From these measurements in neat films, the orientation factor θ was calculated as 0. with PIC-TRZ, demonstrating the link between improved performance and the presence of the phenylene bridge, as both compounds contain the same donor and diphenyltriazine acceptor.