Highly Luminescent Blue Emitter with Balanced Hybridized Locally and Charge‐Transfer Excited‐States Emission

Abstract

In this work, we perform an in‐depth investigation of the optoelectronic properties of a blue emitter (4’’‐(diphenylamino)‐2’’‐methyl‐[1,1’:4’,1’’‐terphenyl]‐4‐carbonitrile), which was reported earlier. Lippert–Mataga analysis of the emission spectra obtained in solvents of varying polarity reveal charge transfer (CT) contributions to the first singlet excited state, S1. Multi‐reference quantum chemical calculations clearly show a balanced local excitation (LE) and CT character of the S1 state and suggests the presence of a LE triplet state, T2, in its energetic vicinity. Finally, organic light emitting diodes (OLED) revealed blue emission at 451 nm and an external quantum efficiency (EQE) of 2 %, corresponding to an internal quantum efficiency (IQE) of circa 10 %.

Balancing TADF Properties in π-Bridged Donor–Acceptor Systems by Sterical Constraints: The Best of Three Worlds

“…This modulating effect is even more pronounced when an additional phenylene bridge is inserted between donor and acceptor, thus increasing their mutual distance. 58 The B-symmetric component of the LE TAA transition can be associated with the S 5 ← S 0 transition. Because its transition dipole vector points in a direction perpendicular to the D−A axis, it cannot couple to a CT excitation.…”

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

“…Our synthetic strategy takes advantage of the one-pot brominelithium 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 terephthalonitrilephenothiazinylene-terephthalonitrile acceptor-donor-acceptor triads 5 (Scheme 2) are synthesized and obtained after chromatographic purification in good to excellent yield.…”

Molecular design of phenazine-5,10-diyl-dibenzonitriles and the impact on their thermally activated delayed fluorescence properties

“…5,6,[14][15][16][17] This high efficiency can be achieved because the lowest excited singlet state (S 1 ) and lowest excited triplet state (T 1 ) are energetically sufficiently close that reverse intersystem crossing (rISC) can be thermally triggered. [18][19][20][21][22][23] The energy difference DE ST of both energy levels is typically less than 0.1 eV for the current highly efficient organic TADF emitters. 14,[24][25][26][27] The smaller the energy gap DE ST between S 1 and T 1 the higher the equilibrium population of the higher excited S 1 state, which governs up to 25% of the internal quantum efficiency in cases of electric injection of charge carriers.…”