Converting Conventional Host to TADF Sensitizer and Hot‐Exciton Emitter in Donor‐Adamantane‐Acceptor Triads for Blue OLEDs: A Computational Study

TADF Sensitizer and Hot-Exciton Emitter: The conventional host molecule undergoes a conversion into a TADF sensitizer and a Hot-Exciton emitter via distinct donor and acceptor unit substitutions on the adamantane core. Molecules incorporating acceptor units such as DMB and BODIPY, which feature boron atoms, have the potential to serve as TADF sensitizers and Hot-exciton emitters for OLED applications, respectively.

Abstract

Exploiting triplet excitons in TADF sensitizers and hot-exciton emitters has attracted considerable attention and interest in recent studies on the design and development of blue OLEDs. The structural and optical property relationship of adamantane (Ad) core appended with four different strengths of donor and seven acceptor units were investigated using DFT and TD-DFT methods. The theoretical studies revealed that increased donor and acceptor strength on adamantane building block leads to: (i) a decrease in ionization potentials and an increase in electron affinities, (ii) a decrease in singlet energies (E_S) and the S₁-T₁ energy gaps (ΔE_ST); (iii) decreased SOC magnitudes between S₁-T₁ states; (iv) increased RISC rate from the T_n to S₁ states, demonstrating an increased tendency for upconversion of triplet excitons from the T_n to S₁ state. In addition, low exchange energy causes excited state characteristics of molecules to shift from HLCT to CT nature in the S₁ state. In contrast, the T₁ states retain their LE character, resulting in higher triplet energies (E_T). The adamantane molecular systems appended with P-DMAC-Donor-Ad-P-DMB and Donor-Ad-P-BODIPY based triads exhibit promising TADF sensitizer and hot-exciton characteristics to find application as potential candidates for blue OLEDs when compared to experimentally reported conventional host.

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