Inverted CdSe–ZnS quantum dots light-emitting diode using low-work function organic material polyethylenimine ethoxylated

Inverted quantum dot based light-emitting diodes (QDLED) were simply fabricated by an all solution processing. Polyethylenimine ethoxylated (PEIE) was used as a surface modifier in the device, to reduce the indium tin oxide (ITO) electrode work function below 3.08 eV. Based on transmission electron microscopy (TEM) results, CdSe–ZnS QDs with an 8 nm size were uniformly distributed to form a monolayer on a PEIE/ITO glass substrate. In this inverted QDLED, hybrid polymers [poly(N-vinylcarbazole) + poly(N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine were adopted as a hole transporting layer (HTL) to enhance the hole transport property. At a low-operating voltage of 3 V, the device was turned on and emitted a spectrally red color light with a maximum luminance of 2900 cd m−2 and a current efficacy of 0.35 cd A−1.