As a result of the improved charge balance, the EQE of the optimized device not only reached a similar EQEmax of 28.4%, but also maintained its efficiency of 22.7% at a luminance of 500 cd m -2 . A related work documents a detailed photophysical investigation to rationalize the structureproperty relationship of the TADF dendrimers tBuCz3pTRZ and tBuCz3mTRZ (the DFT optimized structures without peripheral tertbutyl groups are shown in Figure ). Both dendrimers exhibit high FPL values (89% for tBuCz3pTRZ and 81% for tBuCz3mTRZ, 10 wt% doped in mCP). While tBuCz3mTRZ (2.92 eV) possesses a slightly higher S1 state than that of tBuCz3pTRZ (2.84 eV) due to the weak electron coupling of meta-connection, both have a similarly small ΔEST (0.1 eV for tBuCz3pTRZ and 0.08 eV for tBuCz3mTRZ). The activation energy barriers (𝐸 !"# ) for RISC are approximately half those of the corresponding Δ𝐸 $% values. However, the contribution of the delayed emission to the total emission (19% for tBuCz3pTRZ and 63% for tBuCz3mTRZ) and the kRISC (0.5×10 5 s -1 for tBuCz3pTRZ and 3.7×10 5 s -1 for tBuCz3mTRZ), both reflecting the efficiency of the RISC process, are much greater/faster in the case of the meta-connected dendrimer tBuCz3mTRZ. orbital coupling (SOC) matrix element was found to be higher for Cz3mTRZ (0.53 cm -1 ) as compared to Cz3pTRZ (0.31 cm -1 ). The intramolecular (𝜆 '(#)! ) reorganization energy for Cz3pTRZ (275 meV) was also calculated to be higher than that of Cz3mTRZ (155 meV).