Hybrid MoS2/PEDOT:PSS transporting layer for Interface Engineering of Nanoplatelets based Light-Emitting Diodes

Colloidal semiconductor nanoplatelets (NPLs) are a subgroup of quantum confined materials that have recently emerged as promising active material for solution processed light-emitting diodes (LEDs) thanks to their peculiar structural and electronic properties as well as their reduced dimensionality. Nowadays the conventional structure for NPL-based LEDs makes use of the poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as hole transporting layer (HTL). This is a well-known conjugated conductive polymer because it leads to high LED’s efficiencies, though it has limited stability in air due to its intrinsic acidity and hygroscopicity. Here, we develop a nanocomposite aqueous ink, obtained by blending commercial PEDOT:PSS with water-based, stable and highly concentrated molybdenum disulfide (MoS2) nanosheets, obtained by Liquid Phase Exfoliation (LPE) suitable as HTL for solution processed NPLs-based LEDs. We demonstrate that the MoS2 additive effectively works as a performance booster in unpackaged devices therein prolonging the lifetime up to 1000 hours upon exposure in ambient conditions. Moreover, the addition of MoS2 induces a modification of the anode interface properties, including a change in the work function and a significant enhancement of the permittivity of the HTL.