The schematic energy level diagram of WOLEDs with the portion of EMLs. (a) device A. (b) device B. (c) device C. Black circle and white circle express electron and hole, respectively. The numbers indicate the LUMO and HOMO energies relative to vacuum (in eV). Here, LUMO and HOMO are cited from [18-20].
Zhao et al. Nanoscale Research Letters 2013 8:529 doi:10.1186/1556-276X-8-529