Luminescence enhancement and emission color adjustment of white organic light-emitting diodes with quantum-well-like structures

Abstract

In recent years, white-light organic light-emitting diodes (OLEDs) have attracted considerable attention because of their potential applications in displays, backlight units, and general lighting. In this paper, we describe the fabrication of a high-luminance white-light OLED with dual-emission layers (EMLs). The 2,9-dimethyl-4,7-diphenyl-1,10-phenanhroline hole blocking layers (HBLs) were prepared to enhance the luminance and adjust the emission color of the device. For the device with a single-HBL structure, the excess holes were accumulated at the red EML (REML)/HBL1 interface. Consequently, most of the carriers were recombined in the REML, which led to a redshifted light emission. On the contrary, the device with a dual-HBL structure showed a blueshifted light emission. The device with a quantum-well-like structure increased the carrier trapping and recombination probabilities; as a result, a lower current density and a higher luminance intensity of the device were achieved. The maximum luminance intensity was 33 600 cd/m2 at 13 V, with CIE coordinates at (0.32, 0.32); the maximum current efficiency was 7.06 cd/A at 10 V; and the maximum power efficiency was 2.62 lm/W at 7 V and 294 cd/m2.