Enhanced Reverse Intersystem Crossing: Quantum Insights into Boron Containing Emitters for Organic Light Emitting Diode Application
DOI:
https://doi.org/10.64296/vijir.v2i1.11Keywords:
Reverse Intersystem Crossing, Boron Containing Emitters, Thermally Activated Delayed Fluorescence Organic Light Emitting Diode, Spin-Orbit Coupling Matrix ElementAbstract
Thermally activated delayed fluorescence (TADF) materials have emerged as promising candidates for next-generation organic light-emitting diodes (OLEDs) due to their ability to harvest both singlet and triplet excitons without requiring heavy metals. In this work, a series of boron-based emitters were investigated to explore the effect of donor substitution on their electronic and excited-state properties. The parent molecule, a boron-oxygen fused molecule 5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracene (BA), was systematically modified with various donor moieties like acridine and carbazole derivatives to form TBA-Ac, TBA-3Cz, TBA-P3Cz, BBAC-Ac and BBAPCAc. The structural optimization, frontier molecular orbital analysis and excited-state characterization of these emitters collectively revealed that donor incorporation strongly influences the singlet-triplet energy separation and spin-orbit interaction, which are critical for efficient reverse intersystem crossing (RISC). The parent compound BA exhibited a large singlet-triplet gap, prohibiting RISC and eliminating TADF behaviour. In contrast, the donor-substituted derivatives showed significantly reduced ΔEST values enabling effective thermal upconversion. TBA-Ac demonstrated the smallest ΔEST (0.12 eV) and the highest SOCME (1.54 cm⁻¹), resulting in the fastest kRISC (1.26 × 10⁶ s⁻¹), establishing it as the most efficient TADF candidate. BBAPC-Ac also showed strong SOC (1.19 cm⁻¹) and high kRISC (4.04 × 10⁵ s⁻¹), confirming that acridine-carbazole donor combinations effectively promote singlet-triplet conversion. The results demonstrate that strategic donor engineering around the boron–oxygen core can effectively accelerate the RISC process. Ultimately, this work establishes a clear structure-property relationship, offering a rational design strategy for developing high-performance, metal-free TADF emitters for next-generation OLED applications.
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