Intersystem Crossing Processes in TADF Emitters

Effective models for TADF: the role of the medium polarizability

“…However, in the hypothesis that the population of the three triplet states is instantaneously equilibrated, the effective RISC rate, to be compared with experiment, must be divided by a factor of 3. 50 Accordingly, we estimate the effective RISC rate for DMAC–TRZ in a non-polar matrix in the 7 × 10 4 −2 × 10 5 s −1 range, in line with experimental results falling in the range 2–5 × 10 5 s −1 in non polar matrices (Zeonex and UGH) as well as in toluene solution. 22 ISC rates are estimated of the order of 2 × 10 6 s −1 approximately one order of magnitude smaller than experimental results (∼2 × 10 7 s −1 ).…”

Design of Conformationally Distorted Donor–Acceptor Dyads Showing Efficient Thermally Activated Delayed Fluorescence

“…Moreover, as recently discussed in detail, also vibronic coupling can induce distinct ISC. 39,40 However, a quantitative approach is not in the scope of this investigation. also decay values.…”

Design strategies for materials showing thermally activated delayed fluorescence and beyond: Towards the fourth‐generation OLED mechanism

“…However, the mixings of 3 LE state by configuration interaction (CI) with the 3 CT state and by SOC with the 1 CT state are weak. Additionally, vibronic coupling can also alter the pure character of the 1,3 CT states . In conclusion, already the discussed weak admixtures of different state character will provide some allowedness to the ISC processes and induce sufficient admixtures to allow for the TADF occurrence in the emission of compound 2 .…”

“…For example, cooling from T = 300 to 200 K red‐shifts the CT emission by ≈10 3 cm −1 (125 meV) due to an increase of polarity. Moreover, vibronic coupling, not discussed here further, opens additional coupling routes …”

“…Accordingly, other electronic states have to be introduced, when developing adequate TADF molecules. Such states can exhibit direct and/or vibronically induced couplings and, thus, enhance ISC rates …”