Organic Electroluminescent Device with Interface Exciplex

The patent introduces a TADF material as an intermediary sensitized material that mediates energy transfer between the fluorescent dye and triplet excitons. The TADF material with small singlet-triplet energy gap facilitates Reverse Intersystem Crossing, converting triplet excitons to singlet excitons that can then transfer energy to the fluorescent dye, enabling efficient utilization of previously wasted triplet excitons while maintaining fluorescent emission characteristics.

The patent changes the energy level parameters of the light-emitting layer by selecting a TADF material with specifically small singlet-triplet energy gap (ΔEST). This parameter change enables the Reverse Intersystem Crossing process to occur efficiently at room temperature, allowing triplet excitons to be converted to singlet excitons and subsequently transfer energy to the fluorescent dye, thereby achieving high internal quantum efficiency without using heavy metal atoms.

The patent replaces expensive heavy metal atoms with organic TADF materials that have relatively short excited state lifetimes but achieve the same function of enabling triplet-to-singlet conversion. The TADF material acts as a temporary mediator that facilitates exciton conversion and then transfers energy to the fluorescent dye, achieving high efficiency without the need for costly noble metal elements like iridium or platinum.

The patent substitutes the heavy atom effect (mechanical/nuclear approach) with a molecular design approach using TADF materials. Instead of relying on the nuclear mass of heavy metals to induce spin-orbit coupling, the patent uses carefully designed organic molecules with specific HOMO-LUMO energy level configurations to achieve the same physical effect through electronic structure engineering, thereby eliminating the need for expensive heavy metal elements.