Excited-State Descriptors for High-Throughput Screening of Efficient Electro-Fluorescent Materials

Electro-fluorescent materials with 100% internal quantum efficiency (IQE) and short fluorescence lifetimes (tau f, similar to ns) are desirable and achievable by harvesting high-lying triplet excitons. However, the IQE governed by exciton utilization efficiency (EUE) and photoluminescence quantum yield (PLQY) remains low. Herein, from the electro-fluorescence process involving triplet excitons and energy gap law, we established two excited-state descriptors (triplet-triplet energy gap Delta ETT and oscillator strengthf) to characterize EUE, PLQY and tau f, by taking a series of hot exciton compounds as prototypes. Subsequently, these descriptors were employed to perform high-throughput screening of over 5000 fluorophores, predicting 19 candidate molecules with a high IQE (>90%). We stressed that the large values of these descriptors are conducive to high EUE and PLQY and short tau f. This work presents a guideline to design and screen efficient electro-fluorescent materials beyond the spin-statistical limit.