Singlet harvesting copper-based emitters: a modular approach towards next-generation OLED technology

Zink, Daniel M.; Bergmann, Larissa; Ambrosek, David; Wallesch, Manuela; Volz, Daniel; Mydlak, Mathias

doi:10.1088/2053-1613/1/1/015003

Cited by 16 publications

(10 citation statements)

References 43 publications

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“…Hence, the TADF effect for an electro-luminescent device has been denoted as singlet harvesting effect. [2][3][4][5]32,44,45,61,65,68,69,[71][72][73]87,88,92,135] (Compare footnote 1. ) For OLED use, the TADF decay time (TADF) is crucial and should be as short as possible, obviously at high emission quantum yields.…”

Section: Thermally Activated Delayed Fluorescence and Singlet Harvestingmentioning

confidence: 99%

Cu(I) complexes – Thermally activated delayed fluorescence. Photophysical approach and material design

Czerwieniec

Leitl

Homeier

et al. 2016

Coordination Chemistry Reviews

490

653

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Cu(I) complexes often show transitions of distinct metal-to-ligand charge transfer (MLCT) character. This can lead to small energy separations between the lowest singlet S1 and triplet T1 state. Hence, thermally activated delayed fluorescence (TADF) and, if applied to electroluminescent devices, singlet harvesting can become highly effective. In this contribution, we introduce the TADF mechanism and identify crucial parameters that are necessary to optimize materials' properties, in particular, with respect to short emission decay times and high quantum yields at ambient temperature. In different case studies, we present a photophysical background for a deeper understanding of the materials' properties. Accordingly, we elucidate strategies for obtaining high quantum yields. These are mainly based on enhancing the intrinsic rigidity of the complexes and of their environment. Efficient TADF essentially requires small energy separations E(S1-T1) with preference below about 1000 cm 1 (≈ 120 meV). This is achievable with complexes that exhibit small spatial HOMO-LUMO overlap. Thus, energy separations below 300 cm 1 (≈ 37 meV) are obtained, giving short radiative TADF decay times of less than 5 s. In a case study, it is shown that the TADF properties may be tuned or the TADF effect can even be turned off. However, very small E(S1-T1) energy separations are related to small radiative rates or small

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Section: Thermally Activated Delayed Fluorescence and Singlet Harvestingmentioning

confidence: 99%

Cu(I) complexes – Thermally activated delayed fluorescence. Photophysical approach and material design

Czerwieniec

Leitl

Homeier

et al. 2016

Coordination Chemistry Reviews

490

653

View full text Add to dashboard Cite

show abstract

“…[1][2][3][4][5] They are easily synthesized 6,7 and tunable in emission color, [8][9][10] with high emission quantum yields in the solid state. 7,10,11 Copper(I) halide compounds can be considered as a valid alternative to luminescent metal complexes of precious (i.e.…”

mentioning

confidence: 99%

Dual luminescence in solid CuI(piperazine): hypothesis of an emissive 1-D delocalized excited state

Maini

Braga

Mazzeo³

et al. 2015

Dalton Trans.

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Solid [CuI( piperazine) 0.5 ] ∞ , characterized by a structure with an infinite double chain of CuI, presents an unexpected dual luminescence. The short copper-copper distances allow the existence of both cluster-centered and 1-D delocalized electronic transitions, as emerged from theoretical calculations. Beyond the more common cluster-centered emission a higher energy band, which differs in lifetime and in temperature dependence, is observed.One of the most prominent classes of luminescent coordination compounds is that of copper(I) halides, due to their promising features for application in the field of optoelectronics. [1][2][3][4][5] They are easily synthesized 6,7 and tunable in emission color, [8][9][10] with high emission quantum yields in the solid state. 7,10,11 Copper(I) halide compounds can be considered as a valid alternative to luminescent metal complexes of precious (i.e. Ir or Os) and rare earth metals, which are expensive and environmentally problematic. 12 The luminescence properties of the copper halide clusters arise from a remarkable variety of emissive states, which have been extensively investigated in the last 30 years and can be summarized as follows: (a) a low-energy emission, attributed to a triplet cluster-centered ( 3 CC) excited state, is observed in the case of metal center interactions [13][14][15][16][17][18][19] and is independent of the nature of the ligand engaged in the complex; (b) a highenergy emission, attributed to a triplet halide-to-ligand charge transfer ( 3 XLCT) excited state, may show up in the presence of unsaturated ligands with accessible π-orbitals. 20 Moreover, recent studies have shown that several copper compounds present a thermally activated delayed fluorescence (TADF): Cu(I) halide-bridged compounds with P^N ligands are characterized by (metal + halide)-to-ligand charge transfer ((M + X) LCT) excited states where the low singlet-triplet energy gap allows emission from both the singlet and the triplet excited states, depending on the temperature. [21][22][23] The structure of [CuI( piperazine) 0.5 ] ∞ 24 is characterized by a one-dimensional copper iodide polymeric structure. The infinite double chain of CuI is described as castellated, 25 as shown in Fig. 1a, and the tetrahedral coordination of the copper(I) ions is fulfilled by the bridging piperazine to construct a 3D network (Fig. 1b and c). The inorganic chain is generated by the sequence of an inversion center and 2-fold axis symmetry elements, thus two different copper distances are present (2.771(1) Å and 2.729(1) Å). Although the presence of infinite double chain motifs has been observed in 20 struc-

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“…Relevant literature (AlSalhi et al 2011;Chen and Hwang 2007;Kamtekar et al 2010;Lambeth 2004;Lee et al 2014;Lin 2009;Liu et al 2006;Madhava Rao et al 2013;Park et al 2009;Sebastian et al 2009;Segal et al 2007;So et al 2007;Sun et al 2014;Zink et al 2014) was referred to, and four experts were consulted, to verify the above research fronts. Among the research fronts mentioned above, six derived from bibliographic coupling are identified as important.…”

Section: Comparisonsmentioning

confidence: 99%

A comparative study on detecting research fronts in the organic light-emitting diode (OLED) field using bibliographic coupling and co-citation

Huang

Chang²

2014

Scientometrics

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Research fronts represent areas of cutting-edge study in specific fields. They not only provide insights into current focuses and future trends, but also serve as important indicators for government policymaking with regard to technology. This study employed both bibliographic coupling and co-citation as methods to analyze the evolution of research fronts in the OLED field, and compared the outcomes in order to identify the differences between, and assess the effectiveness of, the two methods in detecting such research fronts. This study indicated that both analytic methods can be employed to track the evolution of research fronts. Compared with co-citation, bibliographic coupling identifies a higher number of research fronts, and detects the emergence of the research fronts earlier, thus showing better performance than co-citation in detecting research fronts.

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Singlet harvesting copper-based emitters: a modular approach towards next-generation OLED technology

Cited by 16 publications

References 43 publications

Cu(I) complexes – Thermally activated delayed fluorescence. Photophysical approach and material design

Cu(I) complexes – Thermally activated delayed fluorescence. Photophysical approach and material design

Dual luminescence in solid CuI(piperazine): hypothesis of an emissive 1-D delocalized excited state

A comparative study on detecting research fronts in the organic light-emitting diode (OLED) field using bibliographic coupling and co-citation

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