Modifying the AIE-TADF chromophore with host-substituents to achieve high efficiency and low roll-off non-doped OLEDs

In this paper, the periphery of aggregation-induced emission-thermally activated delayed fluorescence (AIETADF) chromophore (DPS-PXZ) was modified with host-substituents (DCB, mCP, pPhDCz and mPhDCz). Four self-host TADF emitters, namely DCB-DPS-PXZ, mCP-DPS-PXZ, pPhDCzDPSPXZ and mPhDCzDPSPXZ, were designed and synthesized. Here, the effect of host-substituents with different linking topologies on TADF has been investigated. Among them, the pPhDCz and mPhDCz substituted AIE-TADF emitters have stronger AIE effect than that of DCB and mCP based ones, which due to the larger twist angle between host substituents and DPSPXZ. And then, mPhDCzDPSPXZ and pPhDCzDPSPXZ could obtain the PLQYs of 56% and 55% in the neat film, respectively. The PLQY values were higher than that of DCB-DPS-PXZ (40%) and mCP-DPS-PXZ (47%). Based on these advantages, the maximum EQE and the efficiency roll-off at 1000 cd/m(2) of the non-doped OLEDs were 18.1% and 7.7% for mPhDCzDPSPXZ, 17.1% and 9.9% for pPhDCzDPSPXZ, respectively. However, the maximum EQEs of DCB-DPS-PXZ and mCP-DPS-PXZ based non-doped devices were only 13.9% and 14.7%, respectively. Therefore, the careful modification of the AIE-TADF chromophore by changing host-substituent types and linking positions appropriately was beneficial for the realization of efficient and low efficiency rolloff non-doped OLEDs.