Luminescent Dinuclear Copper(I) Complexes as Potential Thermally Activated Delayed Fluorescence (TADF) Emitters: A Theoretical Study

Abstract

The excited state properties of a series of binuclear NHetPHOS-Cu(I) complexes (NHetPHOS) have been investigated by means of density functional theory (DFT) and time-dependent DFT (TD-DFT). It is shown that experimental trends observed in powder, generally explored via S and T excited state energetics and S ⇔ T intersystem crossing (ISC) efficiency, are hardly analyzed on the basis of excited state properties calculated in solution. Indeed, several local minima corresponding to various structural deformations are evident on the lowest excited state potential energy surfaces (PES) when solvent correction is applied, leading to a four-state thermally activated delayed fluorescence (TADF) mechanism. In contrast, preliminary simulations performed in the solid point to the reduction of nuclear flexibility and consequently to a rather simple two-state model.

P∩N Bridged Cu(I) Dimers Featuring Both TADF and Phosphorescence. From Overview towards Detailed Case Study of the Excited Singlet and Triplet States

“…This effect of combined TADF-phosphorescence emission, suited for decreasing the overall emission decay time, has already been addressed in the literature [ 50 , 51 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 ]. In particular, Cu(I) and Ag(I) dimers, in which the metal centers are linked by P∩N ligands can show this effect [ 34 , 50 , 87 , 90 , 91 , 92 , 93 , 94 , 95 ] and very probably also the complexes reported recently [ 96 ]. To evaluate the class of materials of Cu 2 X 2 (P∩N) 3 complexes (with X = Cl, Br, I), we study eight compounds with respect to their crystal structures and, especially, their emission properties at T = 300 K and 77 K, respectively.…”

Intriguing Effects of Halogen Substitution on the Photophysical Properties of 2,9-(Bis)halo-Substituted Phenanthrolinecopper(I) Complexes

“…Moreover, vibronic coupling effects may contribute to the TADF mechanism in addition to the SOC effects as shown recently for dinuclear Cu(I) complexes. 51 Further modeling of the emissive properties of this class of complexes should include dynamical effects 52 which are beyond the scope of the present study. Moreover, while Cu-Cl and Cu-Br display the usual thermally activated delayed fluorescence mechanism, Cu-I exhibits the opposite behavior (i.e.…”

QM/MM studies on luminescence mechanism of dinuclear copper iodide complexes with thermally activated delayed fluorescence

“…As third generation emitting materials, organic and inorganic compounds with thermally activated delayed uorescence (TADF) have been extensively studied in recent decades. [1][2][3][4][5][6][7][8][9] Due to the use of inexpensive Cu metal, a large variety of luminescent Cu(I) compounds have been investigated since TADF was observed in Cu(I) complexes by Blasse and co-workers in 1980. 10 In addition, TADF Cu(I) materials exhibit certain superior luminescence properties, for example, they harvest all singlets and triplets for the generation of light in organic light emitting diodes (OLEDs).…”