The Role of Vibronic Coupling for Intersystem Crossing and Reverse Intersystem Crossing Rates in TADF Molecules

Czerwieniec

et al. 2018

J. Phys. Chem. Lett.

A highly potent donor-acceptor biaryl thermally activated delayed fluorescence (TADF) dye is accessible by a concise two-step sequence employing two-fold Ullmann arylation and a sequentially Pd-catalyzed Masuda borylation-Suzuki arylation (MBSA). Photophysical investigations show efficient TADF at ambient temperature due to the sterical hindrance between the donor and acceptor moieties. The photoluminescence quantum yield amounts to Φ = 80% in toluene and 90% in PMMA arising from prompt and delayed fluorescence with decay times of 21 ns and 30 μs, respectively. From an Arrhenius plot, the energy gap Δ E(S - T) between the lowest excited singlet S and triplet T state was determined to be 980 cm (120 meV). A new procedure is proposed that allows us to estimate the intersystem crossing time to ∼10 ns.

mentioning

confidence: 91%

“…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.…”

mentioning

confidence: 99%

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

Sommer

Czerwieniec

et al. 2018

J. Phys. Chem. Lett.

“…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 .…”

Section: Non‐conjugated Bridges Fixing Donor and Acceptormentioning

confidence: 81%

“…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 …”

Section: Functionalized Donor‐acceptor Bridge: Reduction Of Hyper‐conmentioning

confidence: 99%

See 1 more Smart Citation

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

Yersin

et al. 2018

J Soc Info Display

Design strategies for molecules showing thermally activated delayed fluorescence (TADF) are discussed, and a new emitter concept based on an almost “zero‐energy‐gap” is developed. Thermal activation is not substantial. Applied in an organic light emitting diode, all singlet and triplet excitons are harvested directly in the lowest singlet state without time‐delaying TADF. This landmarking mechanism, being beyond TADF, leads to emission decay times in the sub‐μs range.

6‐1: Distinguished Paper and Invited Paper: Design Strategies for Materials Showing Thermally Activated Delayed Fluorescence and Beyond: Towards the Fourth‐generation OLED Mechanism

Yersin

Symp Digest of Tech Papers

et al. 2018

Design strategies for TADF molecules are discussed and a new emitter concept based on an almost “zero‐energy‐gap” is developed. Thermal activation is not substantial. Applied in an OLED, all singlet and triplet excitons are harvested directly in the lowest singlet state without time‐delaying TADF. This landmarking mechanism, being beyond TADF, leads to emission decay times in the sub‐µs range.