Benchmarking of Density Functionals for the Description of Optical Properties of Newly Synthesized π‐Conjugated TADF Blue Emitters. Issue 16 (19th February 2022)

• Record Type: Journal Article
• Authors: Ivanova, Georgia; Bozova, Nadezhda; Petkov, Nikolay; An, Cunbin; Hu, Benlin; Mutovska, Monika; Konstantinov, Konstantin; Zagranyarski, Yulian; Videva, Vladimira; Yordanova, Adelina; Baumgarten, Martin; Ivanova, Anela
• Is Part Of: Chemistry. Volume 28:Issue 16(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-02-19
• Subjects: blue light emission -- DFT functionals -- donor-acceptor π-conjugated emitters -- long-range exact exchange -- thermally activated delayed fluorescence (TADF); Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.202104411
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: Computational modeling of the optical characteristics of organic molecules with potential for thermally activated delayed fluorescence (TADF) may assist markedly the development of more efficient emitting materials for organic light‐emitting diodes. Recent theoretical studies in this area employ mostly methods from density functional theory (DFT). In order to obtain accurate predictions within this approach, the choice of a proper functional is crucial. In the current study, we focus on testing the performance of a set of DFT functionals for estimation of the excitation and emission energy and the excited singlet‐triplet energy gap of three newly synthesized compounds with capacity for TADF. The emitters are designed specifically to enable charge transfer by π‐electron conjugation, at the same time possessing high‐energy excited triplet states. The functionals chosen for testing are from various groups ranging from gradient‐corrected through global hybrids to range‐separated ones. The results show that the monitored optical properties are especially sensitive to how the long‐range part of the exchange energy is treated within the functional. The accurate functional should also be able to provide well balanced distribution of the π‐electrons among the molecular fragments. Global hybrids with moderate (less than 0.4) share of exact exchange (B3LYP, PBE0) and the meta‐GGA HSE06 are outlined as the best performing methods for the systems under study. They can predict all important optical parameters correctly, both qualitatively and quantitatively. Abstract : Synthesis and computational guidelines based on benchmarking of DFT functionals for new π‐conjugated TADF emitters are reported. The three target compounds were obtained by multistep synthesis, including metal‐catalyzed reactions and functional‐group transformations. The emitters feature electron donors and acceptors moderately coupled through a spacer. The importance of the treatment of long‐range exchange within the functionals and their ability to balance the π‐delocalization of the separate molecular fragments are explicitly outlined.