Multicolor Light-Emitting Layer Stack With Exciplex-Phosphorescence

The patent combines multiple light-emitting layers into a stacked-layer structure where a first light-emitting layer (fluorescence) and a second light-emitting layer (phosphorescence) are vertically arranged. This merging approach achieves multicolor emission (yellow from fluorescence + red from phosphorescence = orange-red overall emission) without requiring separate independent layers for each color, thereby reducing overall device complexity while maintaining color diversity.

The stacked light-emitting layer structure serves multiple functions simultaneously: it generates different emission colors through fluorescence and phosphorescence mechanisms, controls energy transfer between layers, and manages triplet excited state distribution. This multi-functionality allows a single stacked structure to replace what would traditionally require multiple separate functional layers, reducing device complexity.

The patent carefully selects and adjusts the triplet excited energy levels of host materials in both the first and second light-emitting layers. By optimizing these energy level parameters, the patent ensures efficient energy transfer from the fluorescence layer to the phosphorescence layer while minimizing nonradiative deactivation and quenching losses. This parameter optimization allows high phosphorescence emission efficiency without excessive energy loss.

The first light-emitting layer (fluorescence) acts as an intermediary energy transfer mediator to the second light-emitting layer (phosphorescence). This intermediary structure enables controlled energy transfer from the fluorescence emission to excite the phosphorescence material, reducing direct energy loss and quenching that would occur with improper host material selection. The intermediary layer facilitates efficient energy cascading while minimizing nonradiative losses.