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Understanding Solid-State Solvation-Enhanced Thermally Activated Delayed Fluorescence Using a Descriptor-Tuned Screened Range-Separated Functional

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journal contribution
posted on 2018-11-21, 00:00 authored by Chao Wang, Qisheng Zhang
An efficient computational protocol suitable for both solutions and solid films can accelerate the development of efficient thermally activated delayed fluorescence (TADF) emitters aimed at practical application in organic light-emitting diodes (OLEDs). By employing the localized orbital locator (LOL), we establish an efficient descriptor-tuning methodology for the range-separated (RS) and screened range-separated (SRS) functionals with only one single-point calculation. This scheme provides good predictions for 28 charge transfer (CT)-type TADF emitters. Moreover, in comparison to the experimental data, the scheme presents a mean absolute deviation of 0.09 eV for the absorption energies of the lowest excited singlet state (EVA(S1)) in polarizable continuum model (PCM) solution and of 0.10 eV for the energy difference between the lowest excited singlet and triplet states (ΔEST) under static solid-state polarization. Importantly, our results indicate that a significantly polarized S1 is key to realizing the so-called solid-state solvation-enhanced (SSSE) TADF, which is well captured through the screened RS functionals combined with LOL tuning (SLOL tuning). Compared with standard ionization potential (IP) tuning, our scheme significantly reduces the computational cost of the prediction of singlet- and triplet-transition energies for CT molecules. It also provides a reliable approach to evaluate the practical TADF character influenced by solid-state solvation in amorphous organic thin films.

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