Mixed host organic light-emitting devices with low driving voltage and long lifetime

In this letter, we present and analyze the device performance of the mixed host (MH) organic light-emitting devices (OLEDs). The host of the emitting layer (EML) material in this device consists of a hole transport layer (HTL) and an electron transport layer (ETL) fabricated by coevaporation. The bipolar transport characteristic of the MH layer helps to reduce the driving voltage. Device lifetime is increased due to the elimination of the sharp boundary of the HTL/EML interface. Combining the MH structure with a high mobility electron ETL material, bis(10-hydroxybenzo[h]qinolinato)beryllium, the OLED has shown a brightness of 27600cd∕m2 at a driving voltage of 5 V, and a lifetime four times longer than that of a conventional OLED.