Highly efficient tandem OLED based on a novel charge generation layer of HAT-CN/CuPc heterojunction

Abstract

A novel non-doped organic heterojunction (OHJ) composed of HAT-CN and CuPc is proposed to be charge generation layers (CGL) for constructing high efficiency tandem organic light-emitting diodes (OLEDs). The highest current efficiency and external quantum efficiency (EQE) of tandem device with this CGL are 46.3 cd/A and 15.1%, which are 125% and 107% higher than those of single emissive unit OLED, respectively. Furthermore, the tandem device provides better stability. The efficiency roll-off from the maximum to 1000 cd/m2 is 7.2% for the tandem device, which delivers a great improvement compared to that of single emissive unit OLED (21.9%). And CuPc thickness in CGLs merely slightly affects the device performance, because of the tradeoff between improved charge injection and declined transmittance with the increase of the CuPc thickness. The experimental results demonstrate that the organic heterojunction consisting of HAT-CN/CuPc is a feasible CGL for developing high performance tandem OLEDs.