Enhancement of electron injection in polymer light-emitting diodes with a supramolecular insulating nanolayer on the bottom cathode

With the aim of enhancing the electron injection of a polymer light-emitting diode (PLED), a supramolecular insulating nanolayer that reacts with the cathode (Ag) was inserted between the bottom cathode and the emitting material. The PLED threshold voltage (for $1\mathrm{cd}∕{\mathrm{m}}^2$ ) was found to decrease from $5.6\text{to}4.2\mathrm{V}$ as a result of the introduction of the nanolayer. Synchrotron radiation photoelectron spectroscopy results show that inserting the supramolecular insulating nanolayer results in a decrease in the work function of about $0.7\mathrm{eV}$ . This reduction lowers the electron injection barrier and produces an increase in the luminance.