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

Abstract

Electro-fluorescent materials with 100% internal quantum efficiency (IQE) and short fluorescence lifetimes (τf, ∼ 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 ΔE TT and oscillator strength f) to characterize EUE, PLQY and τf, 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 τf. This work presents a guideline to design and screen efficient electro-fluorescent materials beyond the spin-statistical limit.

Near-infrared organic light-emitting materials, devices and applications

“…As both phosphorescent and TADF materials can utilize both singlet and triplet excitons, organic light-emitting devices (OLEDs) made with these materials theoretically have the potential to achieve an internal quantum efficiency (IQE) of 100%. 19,20 However, due to the small band gap of NIR materials, non-radiative decay can be significant according to the energy gap law, resulting in a photoluminescence quantum yield (PLQY) that is often below unity. Therefore, many efforts have been made to reduce the probability of non-radiative decay and greatly improve the PLQY of NIR emitters.…”

2D-Graph of intermolecular interactions predicts radical character of anion–π* type charge-transfer complexes

“…Empirically, whether or not a chemical bond can eventually form depends on both the spatial overlap and symmetry, and the energy difference, between the two interacting MOs. Referring to the idea in the screening of electro-fluorescent materials, 16 the two descriptors can be defined as the following: the overlap integral S DA = 〈 Φ D | Φ A 〉 and the calculated HOMO–LUMO energy difference E DA = E D − E A . For most molecular pairs, we assume that these two orbitals are predominately involved in the bonding process.…”