Highly efficient organic light-emitting devices by introducing traps in the hole-injection layer

We introduced Pt3Co nanoparticles (NPs) into the hole-injection layer (HIL) in organic light-emitting devices and demonstrated a highly efficient green OLED. The Pt3Co NPs as the hole-traps adjusted the hole transport property in the PEDOT:PSS layer, consequently resulting in a balanced charge injection into the emission layer and enhancing the efficiency of the devices. The theory analysis also indicated that the hole traps induced by Pt3Co NPs played an important role in improving the charge balance in the Pt3Co-containing devices. The studies on the transient resolution photoluminescence (TRPL) indicated that the lifetime of the excitons was not influenced by the Pt3Co NPs, even though a very thin spacer was introduced. The Pt3Co-containing device exhibited a 73% higher current efficiency compared with the conventional device without Pt3Co NPs.