Utilization of a phenanthroimidazole based fluorophore in light-emitting electrochemical cells

Neutral free-base and metallo-porphyrins have been successfully used in organic light-emitting diodes (OLEDs) and solar cells. [1][2][3][4][5] This field is mainly driven by their ease of modification to enhance light-harvesting and photoluminescence (PL) properties based on an efficient energy and/or electron transfer process from moieties attached at the periphery to the porphyrin core.This feature of dyad-like porphyrins is of utmost relevance for lighting schemes, since it could open a new avenue to decouple charge transport and emission processes by only using one active compound. This is more critical in light-emitting electrochemical cells (LECs) than in OLEDs, in which the charge transport is not performed by the emitter, but by a multilayered device architecture. 6,7 In LECs, the presence of mobile ions in the active singlelayer assists the charge injection process, while the charge transport, electron-hole recombination, and emission processes occur via the emitter. 8-10 Thus, to define clear guidelines to design LEC materials that are intrinsically able to decouple charge transport and emission is a challenge in the field. 8-10As an alternative, the host-guest approach by (i) using OLED-host materials doped with ionic liquids, 11 (ii) mixtures of iTMCs, 12-14 and (iii) using ionic-based small-molecule charge transporters, 15 has been explored in LECs to date. All these approaches show the typical problem of the host-guest strategy, that is, to determine the optimum doping level and effective doping range, which are typically very low and narrow, respectively. Here, a low doping level causes an inefficient energy transfer (ET) from the host to the guest, resulting in a poor color purity and device performance, while a high concentration of the guest leads to the a strong self-quenching of its emission and a prominent phase separation in thin films. The latter are paramount in determining the overall device performance. Herein, we report on a new concept to decouple charge transport and emission in small-molecule LECs by using only one active compound mixed with an ionic electrolyte. To this end, we took advantage of our mature experience in the synthesis of BODIPYporphyrin dyads and their implementation in solar cells [16][17][18][19] to further expand their application to lighting schemes, in which the above-mentioned drawbacks of the host-guest approach are circumvented. In detail, two BODIPY-porphyrin dyads have been designed -Scheme 1. On one hand, these dyads fulfill all of the key requirements, such as (i) the energy alignment of the electronic levels between the BODIPY and the porphyrin evokes in a chargeScheme 1 Synthesis of BODIPY-porphyrin dyads 1 and 2.

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“…In line with the few reports on SM-LECs, [31][32][33][34] Fig. 3 depicts the typical device response features of ionic-based lighting devices.…”

supporting

confidence: 66%

Benefits of using BODIPY–porphyrin dyads for developing deep-red lighting sources

et al. 2016

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“…Two other compounds are worth mentioning, viz. 9-(1H-benzimidazol-2-yl)-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinoline (VI) (TAQHUR; Gonzalez & Unnamatla, 2017) and 2-(pyren-1-yl)-1H-phenanthro[9,10-d]imidazole unknown solvate (VII) (KUFLOO; Subeesh et al, 2015). In (VI), the mean plane of the pyridoquinoline moiety is inclined to the benzimidole ring system by 37.94 (10) and the bridging C-C bond is 1.467 (3) Å , similar to the situation in (I).…”

Section: Figurementioning

confidence: 99%

Crystal structure and DFT study of 2-(pyren-1-yl)-1H-benzimidazole

2017

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In the title compound, C 23 H 14 N 2 , (I), the dihedral angle between the mean planes of the pyrene and benzimidazole ring systems is 42.08 (5) , with a bridging C-C bond length of 1.463 (3) Å . In the crystal, molecules are linked by N-HÁ Á ÁN hydrogen bonds, forming columns propagating along the b-axis direction. The columns are linked via C-HÁ Á Á interactions, forming slabs parallel to the ab plane. There are no significant -interactions present in the crystal structure. The density functional theory (DFT) optimized structure, at the B3LYP/ 6-311G(d,p) level, is compared with the experimentally determined solid-state structure of the title compound.

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“…EDLs generate strong electrical fields, and the potential drop then compensates the initial mismatch in energy between the Fermi level of the cathode (anode) and the lowest unoccupied molecular orbital (LUMO)/highest occupied molecular orbital (HOMO) level of the organic semiconductor over the EDLs. This peculiar operational mechanism enables the use of air‐stable electrodes, low driving voltages close to the band gap potential of the light‐emitting species used, and the implementation of novel emitting species like perovskites, cyanine dyes, and small‐molecules …”

Section: Introductionmentioning

confidence: 99%

Performance Enhancement by ZnO Nanoparticle Layer in Hybrid Ionic Transition Metal Complex‐Light‐Emitting Electrochemical Cells (iTMC‐LECs)

Marcantonio

Gellner

Namanga

et al. 2016

Adv Materials Technologies

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Light‐emitting electrochemical cells (LECs) are solution processable solid‐state light sources comprising in their simplest architecture an ionic emissive layer in between of two electrodes. Although LECs possess several advantages that make them promising candidates for future large‐area low‐cost lighting technologies, their device wall‐plug efficacies remain so far moderate on the order of a few lumens per watt. One of the reasons therefore is considered to be the charge imbalance within the device. Here, a hybrid LEC device concept is introduced, whereby an additional layer of zinc oxide (ZnO) nanoparticles at the cathode side supports electron injection into the active light‐emitting layer and boosts the performance of the Ir‐based ionic transition metal complex LEC (iTMC‐LEC). The brightness and efficacy of the devices can be increased in average by more than 70% by the implementation of the additional inorganic layer. The time to reach the maximum brightness can be reduced in average by a factor of 7, which is attributed to an improved electron/hole balance in the device due to enhanced electron injection into the active iTMC layer.

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Utilization of a phenanthroimidazole based fluorophore in light-emitting electrochemical cells

Abstract: A phenanthroimidazole derivative is used as an emitter in light emitting electrochemical cells (LECs).

Cited by 69 publications

References 39 publications

Benefits of using BODIPY–porphyrin dyads for developing deep-red lighting sources

Benefits of using BODIPY–porphyrin dyads for developing deep-red lighting sources

Crystal structure and DFT study of 2-(pyren-1-yl)-1H-benzimidazole

Performance Enhancement by ZnO Nanoparticle Layer in Hybrid Ionic Transition Metal Complex‐Light‐Emitting Electrochemical Cells (iTMC‐LECs)

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