Molecular descriptors for high-throughput virtual screening of fluorescence emitters with inverted singlet-triplet energy gaps

The discovery of fluorescence materials with an inverted singlet-triplet (IST) energy gap, where the singlet excited state (S1) lies below the triplet excited state (T1), mark a transformative advancement in organic light-emitting diodes (OLEDs) technology. However, designing the potential IST emitters are greatly challenging, and their IST energy gap, arising from double electron excitation, can only be accurately described by time-consuming post-Hartree-Fock (HF) methods, which blocks large-scale high-throughput screening speed. Here, we develop a four-orbital model to elucidate detailly the roles of double excitations in the IST formation, and establish two molecular descriptors (KS and $${O}_{{\rm{D}}}$$ ) based on exchange integral and molecular orbital energy. By these descriptors, we rapidly identify 41 IST candidates out of 3,486 molecules. The descriptors-aided approach achieves a screening success rate of 90% and reduces computational costs by 13 times compared to full post-HF calculations. Importantly, we predicted a series of excellent non-traditional near-infrared IST emitters from a dataset of 1028 compounds with emission wavelengths ranging from 852.2 to 1002.3 nm, which open new avenues for designing highly efficient near-infrared OLED materials.