Highly Efficient Electron Injection from Indium Tin Oxide/Cross-Linkable Amino-Functionalized Polyfluorene Interface in Inverted Organic Light Emitting Devices

We show that a series of solution processable and cross-linkable amino-functionalized polyfluorene materials can effectively enhance the electron injection from the indium tin oxide (ITO) electrodes, and for the first time, highly efficient inverted organic light emitting devices are fabricated using cross-linkable conjugated polymers as a single electron injection layer without the need for n-type metal oxide layers. The mechanism for the electron injection enhancement effect of the ITO/cross-linkable conjugated polymer interface is studied by X-ray photoelectron spectroscopy, Kelvin probe, and photovoltaic measurement. It was found that the amino groups among these polymers can effectively lower the work function of ITO, which will greatly enhance the electron injection in the resulting devices.