Single walled carbon nanotube anodes based high performance organic light-emitting diodes with enhanced contrast ratio

Commercially-available single walled carbon nanotubes (SWCNTs) were used to fabricate SWCNT sheets for anodes of organic light-emitting diodes (OLEDs) by spray-coating process without any use of surfactant or acid treatment. A layer of DMSO doped PEDOT:PSS was spray-coated on the SWCNT sheets to not only lessen the surface roughness to an acceptable level, but also improve the conductivity by more than three orders of magnitude. For our SWCNT-based OLEDs of tris-(8-hydroxquinoline) aluminum (Alq3) emission layers, a maximum luminance 4224 cd/m2 and current efficiency 3.12 cd/A were achieved, which is close to the efficiency of ITO-based OLEDs. We further found out that our OLEDs based on the PEDOT:PSS covered SWCNT anodes tripled the contrast ratio of the conventional indium tin oxide (ITO) based OLEDs.

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► Commercially-available SWCNTs were used as anodes to construct OLEDs.
► High quality SWCNT sheets were fabricated easily by spray-coating process.
► PEDOT:PSS layers greatly improved conductivity and roughness of SWCNT anodes.
► High efficiency of our SWCNT OLEDs was achieved, close to that of the ITO OLEDs.
► PEDOT:PSS-covered SWCNT sheets considerably enhanced contrast ratio of OLEDs.