Rational Design\nof Organic Emitters with Inverted\nSinglet–Triplet Gaps for Enhanced Exciton Management

In organic light-emitting diodes (OLEDs), the pursuit\nof efficient\nmolecular emitters has led to the development of thermally activated\ndelayed fluorescence (TADF) molecules. While TADF compounds have promising\nproperties, they face challenges such as energy gap constraints and\nuphill exciton transfer. Inverted emitters (INVEST) offer a novel\nsolution with an inverted singlet–triplet energy (Δ<i>E</i><sub>ST</sub>) gap, enabling efficient utilization of excitons.\nThis study examines the design and computational analysis of an array\nof molecules, including 23 INVEST emitters and remaining with positive\nenergy gaps. Within the STEOM-DLPNO–CCSD framework, we explore\nthe role of various molecular fragments in determining Δ<i>E</i><sub>ST</sub>. We also assess the importance of dynamic\nspin-polarization (DSP) obtained via the Pariser–Parr–Pople\n(PPP) scheme in energy gap determination. Exciting trends emerged\nfrom our results, with pentalene-containing compounds consistently\nmanifesting negative Δ<i>E</i><sub>ST</sub> values\nwhile their naphthalene counterparts exhibited contrasting behavior.\nMoreover, we observed a negative DSP correlates with inverted singlet–triplet\ngaps. Overall, this research advances OLED materials through molecular\ndesign and computational analysis, offering avenues for optimizing\nexciton management and enhancing device performance.