11.1: Invited Paper: High Performance Deep Red OLEDs Using Dual p‐dopants to Control Hole Injection

We demonstrate improved charge balance in organic light emitting devices (OLEDs) by optimizing the hole injection layer (HIL) to control the hole density through the device. Two novel p‐dopants (PDs), PD02 with a shallow lowest unoccupied molecular orbital (LUMO) at ‐4.63 eV (reported in our previous work) and PD03 with a relatively deep LUMO of ‐4.91 eV were used. A two‐layer HIL consisting of HTM:PD02 and HTM:PD03 introduces new design flexibility to improve charge balance in the light emission layer. Using 16% by mass of PD02 and 3% by mass of PD03, we achieve, (1) a bottom emission deep red device with an external quantum efficiency (EQE) of over 30% at a CIE of (0.701, 0.299), an operating voltage of 3.2 V and LT₉₅~13, 000 h at 10 mA/cm². In particular, the efficiency roll‐off of this device is greatly reduced, which is highly desirable in the display industry. (2) a top emission deep red device with a current efficiency (CE) of 75 cd/A at a CIE of (0.707, 0.293), an operating voltage of 3.6 V and LT95 over 15, 000 h at 10 mA/cm². An additional benefit from this novel dual p‐doped HIL approach is its much lower lateral conductivity compared to the standard single HIL device structure, resulting in reduced lateral crosstalk between RGB pixels.