Study on organic light-emitting device with more balanced charge transport

In this paper, we present the device performance of N4,N4'-Di-naphthalen-2-yl- N4, N4'-di-naphthalen-1-yl-biphenyl-4,4'-diamine (TNB) as the HTL material and bis(10-hydroxyben-zo[h]quinolinato) beryllium (Bebq2) as the ETL material. The mobility of TNB and Bebq2 is at the same order of magnitude from our time of flight (TOF) measurement. Therefore, a device with more balanced carrier transport leads to better device performance. At 10 mA/cm2, the drive voltage of the devices is as low as 3.16 V since the use of the high mobility ETL, Bebq2. The voltage variation when changing HTL thickness is nearly the same as that when changing ETL thickness. That shows the voltage drop is higher on HTL than ETL due to the use of high mobility ETL material. That also leads to the more balanced carrier transport than that in a conventional OLED. We also observed that a thinner device has longer operation lifetime that may be due to fewer traps in such a device.