OLED Host-Dopant Energy Alignment for Exciton Confinement

The patent optimizes the energy gap parameter between host and dopant to achieve a balance: sufficiently large to enable effective carrier injection but controlled to prevent excessive driving voltage. This involves selecting host and dopant materials with specific energy level alignments that satisfy both requirements simultaneously.

The emission layer is segmented into distinct host and dopant components with specific energy level relationships. The host material provides triplet energy that is higher than the dopant, creating energy barriers that confine triplet excitons to specific regions and prevent their diffusion, thereby maintaining high light emission efficiency while enabling controlled energy transfer to the dopant for phosphorescent emission.

The patent applies local quality by creating specific energy level configurations in different regions of the emission layer. The host material is selected with locally higher triplet energy to prevent exciton diffusion in certain zones, while maintaining appropriate energy offsets in other regions to facilitate efficient energy transfer to the dopant. This spatial variation in energy level properties resolves the contradiction between exciton confinement and energy transfer.