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.