Effect of exciton-blocking layer on the characteristics of multilayer white organic light-emitting diodes

In this study, the effect of exciton-blocking layer (EBL), employed between the electron-transporting layer (ETL) and the undoped host spacer layer, on the characteristics of fluorescent/phosphorescent multilayer white organic lightemitting diode (OLED) is investigated numerically with the APSYS (Advanced Physical Model of Semiconductor Devices) simulation program. The validation of simulation model is confirmed by the good agreement of photoelectric characteristics between the results obtained numerically and those obtained experimentally. Simulation results suggest that singlet excitons and triplet excitons are generated at both hole-transporting layer (HTL)/emitting layer (EML) and EML/ETL interfaces, where electrons and holes accumulate and recombine, with certain thickness of host spacer layers employed on both sides of EML of white OLED structure. Further study shows that a better choice for the trade-off between color stability and electroluminescence (EL) efficiency can be achieved by properly adjusting the number of EBLs. An optimized performance is achieved if two pairs of EBLs are used.