Organic Light-Emitting Diodes with Low Turn-On Voltages and Improved Stability Featuring a PTCDI-C13:CuPc Mixed Hole Injection Layer

Abstract

We report herein that a mixed layer of the electron-donating copper phthalocyanine (CuPc) and electron-accepting N,N'-ditridecyl perylene diimide (PTCDI-C13) can be an efficient hole injection layer (HIL) for high-performance organic light-emitting diodes (OLEDs). From photophysical, morphological, and structural studies combined with electrical analysis based on the Mott-Schottky model, we conclude that the excellent miscibility between CuPc and PTCDI-C13 enables highly efficient charge transfer, and thus effective p-doping of CuPc, leading to increased hole conductivity of the HIL. As a result, turn-on voltages as low as 2.45 V and greatly improved thermal stabilities as compared to those of OLEDs with conventional CuPc HILs are observed.