19‐1: Invited Paper: P‐Dopant with Ultra‐Low Conductivity Used in Tandem OLEDs

In this work, we report a novel p‐dopant (PD) material, PD03, designed to minimize lateral leakage current while maintaining excellent device performance in tandem OLEDs, and compare its performance to previous materials PD01 and PD02. PD03 has a LUMO energy level at ‐5.07 eV, which is comparable to the other PDs. A hole injection layer (HIL) is demonstrated by co‐depositing the PDs with a hole transport material (HTM) having a HOMO level at ‐5.13 eV. A p‐type charge generation layer (p‐CGL) is also demonstrated. Single‐unit, top‐emitting, fluorescent blue OLEDs using the PDs in the HIL show substantially equivalent device performance using 8% doping concentration by weight of PD03 as those with 3% PD01 and 02. A PD03‐doped film shows lower absorption in the 400 – 500 nm wavelength range than the other PDs, which is particularly beneficial for blue OLEDs. Two‐unit top‐emission blue OLEDs incorporating various PDs in the p‐CGL and 3% PD02 in HIL achieve comparable efficiency, operating voltage, and lifetime as those using commercial PDs. Compared to a single‐unit device that uses 3% PD02 in the HIL, a tandem device with 10% PD03 in a p‐CGL shows 1.8x higher efficiency and 2.1x longer lifetime, with < 1.8x higher voltage. Moreover, an HTM doped with PD03 exhibits ultra‐low lateral conductivity across a wide range of doping concentrations with a conductivity of only 1.2×10 ‐4 S/m at 10% doping, which is at least one order of magnitude lower than similar devices using PD01 and 02. This demonstrates that PD03 provides efficient charge injection as a p‐CGL and, more importantly, reduced crosstalk between pixels, as compared to conventional p‐dopants. These findings establish PD03 as a promising candidate for tandem OLEDs, the building blocks for next‐generation high quality displays.