Engineering emissive excited states in organic electroluminescent materials

The progress of full-color displays and solid-state lighting technology is greatly promoted by the rapid development of cutting-edge research on the design of organic luminescent materials and device architecture. The nature of the excited state plays a central role in governing the photophysical properties of the emitters, which then determine the performance of the organic electroluminescence. This review presents the engineering of emissive excited states in organic luminescent materials toward highly efficient electroluminescence. The fundamentals of electroluminescence and a discussion of excited-state engineering of organic electroluminescent materials are presented. From the perspective of spin multiplicity of the excited state, representative breakthroughs in molecular design strategies for triplet excited-state-utilizable emitters and doublet excited-state-based ones, as well as their application in high-performance electroluminescence, are discussed. Finally, we provide perspectives to emphasize the current challenges and potential opportunities for further development of high-performance electroluminescent materials.