Carbon nanotube modified electrodes for enhanced brightness in organic light emitting devices

Acid oxidised multiwall carbon nanotubes (COOH-MWCNT) have been introduced as a hole injection buffer layer in an organic light emitting diodes (OLED). We show that the OLED with COOH-MWCNT as a buffer layer provides higher brightness with lower operating voltages. The addition of a COOH-MWCNT buffer layer has enabled a further increase in the brightness of our OLED devices operating in excess of 20,000 cd/m2 due to enhanced hole injection by several orders of magnitude. The increase in current injection and brightness does not alter the optical emission spectrum at different operating voltages in these devices. A model is proposed to explain this increase in current injection and brightness based on the modified electron energy band alignment.