InP-Based Quantum Dot Light-Emitting Diode with a Blended Emissive Layer

We fabricated a homogeneous thin film by blending a hole-transporting organic molecule having long alkyl chains, N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)-9,9-dioctylfluorene (DOFL-TPD), with InP/ZnSe/ZnS quantum dots (QDs) and used it as an emissive layer (EML) in a light-emitting diode (LED). The blended QD EML-based device exhibited an external quantum efficiency of 18.6% and a maximum luminance of 128 577 cd/m(2). Additionally, its operational lifetime significantly increased in comparison to that of the control devices without DOFL-TPD. We found that the uniform distribution of DOFL-TPD in the blended QD EML without any phase separation facilitated hole injection into the EML and energy transfer to QDs. Moreover, it was newly discovered that the blended QD EML suppressed electron injection into the hole transport/injection layers, thereby preventing structural degradation of the device. The homogeneously blended QD layer with an efficient charge transport material shows a strong potential to develop efficient and stable optoelectronic devices with balanced charge density.

Automated summary

Blending hole-transporting organic molecule DOFL-TPD with InP/ZnSe/ZnS quantum dots, a homogeneous thin film was fabricated as the emissive layer for an LED. The blended QD EML-based device showed high external quantum efficiency and maximum luminance, with significantly increased operational lifetime. The uniform distribution of DOFL-TPD facilitated charge injection and transfer, while suppressing electron injection to prevent structural degradation of the device.