Enhanced thermal stability of OLEDs based on an organic n–p heterojunction and its derivative

Abstract To address the issues of insufficient thermal stability in charge generation layers (CGLs) and carrier imbalance induced by high-temperature annealing in organic light-emitting diodes (OLEDs), this study proposes a metal oxide-doped organic n–p heterojunction (BPhen:Ag 2 O/NPB:MoO 3 ) as the core functional layer and designs novel device structures based on its derivatives. By analyzing the performance evolution of heterojunction thin films and OLEDs under annealing treatments ranging from 27 °C to 100 °C, it was found that after high-temperature annealing, the surface MoO 3 particles became uniformly dispersed in the heterojunction films, with reduced roughness and no crystallization observed, demonstrating excellent thermal stability. Single-carrier device tests revealed that the current density reached its maximum value at 80 °C annealing. In comparison, at 100 °C annealing, the current density decreased due to the dissociation of charge-transfer complexes (CTCs), yet it remained higher than that under ambient conditions. Furthermore, the performance degradation of the newly developed p–i–n–p structure OLEDs after high-temperature annealing was significantly smaller compared to conventional p–i–n structures.