Using self-assembled monolayers to modify electrode interfaces in organic light-emitting diodes

The energetic and distance dependence of charge injection of organic light-emitting diodes (OLEDs) is studied by modifying the electrodes surface with a series of self-assembled monolayers (SAMs). The compounds used are alkane thiols, having a variety of carbon chain lengths and terminated by different electro-active groups. Conjugated polymer light emitting diode (PLED) devices are fabricated on a semi-transparent gold anode. The application of SAMs results in a decrease in current density and in light output relative to control samples. This suggests that the longer the alkane chain, the lower current and radiance at any voltage level of the SAM treated electrodes.