Efficient near ultraviolet organic light-emitting diode based on PVK material doped with BCPO molecules

Near ultraviolet organic light-emitting diodes (NUV-OLEDs) have a wide range of applications. However, when large band-gap polymer of PVK was used as the emitting material, its poor electron transportation capability resulted in a large amount of charge accumulation on both sides of light-emitting layer/electron-transporting layer interface of the device, hence generating intense electroplex emission and seriously reducing the efficiency of NUV light-emitting. In order to solve this issue, BCPO molecules were doped in PVK with certain concentrations, forming PVK:BCPO mixing light-emitting layers. As compared with pure PVK, electron transportation capability was apparently increased in PVK:BCPO mixing layers. On one hand, charge accumulation at the interface was substantially weakened, and the electroplex emission was inhibited. On the other hand, transportations of electron and hole carriers became more balanced in light-emitting layer. Both of these improvements effectively promoted device performance. At appropriate BCPO doping concentration, the external quantum efficiency of PVK:BCPO-based NUV-OLEDs reached the maximum value of similar to 2.6 %. Further experimental progress would bring it closer to the practical application in future.