Ultrathin sol–gel titanium oxide hole injection layer in OLEDs

In this work, we report an application of sol–gel process in the fabrication of OLEDs. The hole injection efficiency was improved tremendously by inserting an ultrathin sol–gel titanium oxide buffer layer between the ITO anode and hole transport layer. The turn-on voltage of the device with the buffer layer was lowered from 10 V to 3.1, and the operating voltage (at 200 cd/m2) from 13.8 to 6.4 V, compared with the device without such a buffer layer. These devices demonstrated a maximum luminance of ∼40,000 cd/m2. The mechanisms behind the enhanced performance were discussed.