A Thermally Activated Delayed Fluorescence Emitter Investigated by Time‐Resolved Near‐Infrared Spectroscopy

Abstract

Emitters for organic light‐emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) require small singlet (S1)‐triplet (T1) energy gaps as well as fast intersystem crossing (ISC) transitions. These transitions can be mediated by vibronic mixing with higher excited states Sn and Tn (n=2, 3, 4, …). For a prototypical TADF emitter consisting of a triarylamine and a dicyanobenzene moiety (TAA‐DCN) it is shown that these higher states can be located energetically by time‐resolved near‐infrared (NIR) spectroscopy.

3‐Ligated Phenothiazinyl‐terephthalonitrile Dyads and Triads ‐ Synthesis, Electronic Properties, Delayed Fluorescence and Electronic Structure

“…Our synthetic strategy takes advantage of the one‐pot bromine‐lithium exchange‐borylation‐Suzuki (BLEBS) sequence, [13] which has just recently applied to the efficient syntheses of deep‐blue terphenyl emitters [14] and to the synthesis of the parent diphenylamino‐ ortho ‐xylyl‐terephthalonitrile TADF emitter dyad [12a] that was employed in NIR‐spectroscopic and quantum chemical assignments of transitions within the excited states [12b] . Starting from 3‐bromo phenothiazines 1 or 3,7‐dibromo phenothiazines 4 the series of phenothiazinyl‐terephthalonitrile donor‐acceptor dyads 3 (Scheme 1) and terephthalonitrile‐phenothiazinylene‐terephthalonitrile acceptor‐donor‐acceptor triads 5 (Scheme 2) are synthesized and obtained after chromatographic purification in good to excellent yield.…”

The slow photo-induced CO2 release of N-phthaloylglycine

“…The femtosecond transient UV/vis absorption setup was described in detail elsewhere. [37][38][39] The 300 nm pump pulses were obtained from the output of a Ti:Sa laser amplier system (Coherent Libra, output 800 nm, repetition rate of 1 kHz, pulse duration of 100 fs (FWHM)). Part of its output was converted by a noncollinear OPA (TOPAS-white, Light Conversion) to 600 nm and subsequently the frequency was doubled in a b-barium borate crystal to obtain 300 nm pulses.…”

Increasing the Fluorescence Quantum Yield and Lifetime of the Flavin Chromophore by Rational Design

“…Nanosecond transient absorption data were acquired using a transient absorption spectrometer from Edinburgh Instruments in a right-angle geometry (LP980). [53] The excitation source was a Nd: YAG laser (Spitlight 600, InnoLas, repetition rate 5 Hz, pulse duration of 12 ns (FWHM), diameter of the pump beam ~8 mm) with an excitation wavelength of 355 nm which was generated by frequency-tripling. The average pulse energy amounted to 0.5 mJ.…”