BODIPY‐Pt‐Porphyrins Polyads for Efficient Near‐Infrared Light‐Emitting Electrochemical Cells

Abstract

The search for deep-red and near-infrared (NIR) small molecule emitters for solid-state lighting devices is an ongoing quest. [1,2] Among the solid-state lighting approaches, light-emitting electrochemical cells (LECs) are of particular interest as they consist of a simple structure, that is, a layer of ionic and neutral electroluminescent materials with ionic additives, sandwiched between two electrodes. [3,4] The working mechanism involves the initial formation of electric double layers (EDLs) upon applying external bias, leading to an efficient charge injection from air stable electrodes and the subsequent formation of p-and n-doped regions flanking the emitting undoped (i) region, in which hole-electron recombination forms radiative excitons. This working mechanism is named p-i-n junction. Importantly, the device performance does not strictly depend on the electrode material, [5] allowing for low-cost and high-throughput solution-based fabrication under ambient air. [3,[6][7][8] While several red emitters have already been implemented in LECs, [1,3,[9][10][11][12][13][14][15][16][17][18][19][20] the best NIR-emitting LECs rely on ionic transition metal complexes. [9,[21][22][23][24][25][26][27] Here, porphyrins could stand out due to their easy synthesis and modification toward NIR emission. [28] Indeed, several groups have recently shown interesting advances in porphyrin-based LECs. In 2016, our group first reported on the effect of the metal core (Zn 2þ , Sn 2þ , Pt 2þ , and Pd 2þ ), of porphyrins on the LEC figures-of-merit, achieving red-emitting devices that were either stable and low efficient (Zn-porphyrin) or highly efficient but poorly stable (Pt-porphyrin). [17] In detail, Pt-porphyrin-based LECs exhibited good efficiencies caused by the heavy metal-induced phosphorescent emission, but also a pronounced electrochemical degradation, leading to low stabilities of a few minutes. This issue can be overcome using a host-guest system to decouple charge transport and exciton recombination. [11,17] In this context, the chemical binding of host-guest units in a dyad-type structure is desired over simple physical blending toward stable and efficient LECs. [11,15,29] For instance, we reported on intramolecular host-guest systems binding 1 BODIPY (BDP) unit to the periphery of a Zn-porphyrin that yielded deep-red LECs with one order of magnitude enhanced stabilities (>1000 h) keeping the low irradiance of the reference devices with the Zn-porphyrin reference. [11] Edman and coworkers reported on the design and synthesis of a host-guest star-shaped diketopyrrolopyrroleÀZn-porphyrin,

Versatile Biogenic Electrolytes for Highly Performing and Self‐Stable Light‐Emitting Electrochemical Cells

“…In this context, huge efforts have been carried out to introduce ecological emitters in LECs (iTMCs, [ 8,9 ] small molecules, [ 10,11 ] carbon dots, [ 12 ] etc. ), while little consideration has been placed on green ionic electrolytes.…”

“…Thus, the transition toward eco-friendly LECs is becoming urgent to set in its market niche in the short term. [7] In this context, huge efforts have been carried out to introduce ecological emitters in LECs (iTMCs, [8,9] small molecules, [10,11] carbon dots, [12] etc. ), while little consideration has been placed on green ionic electrolytes.…”

Novel Red‐Emitting Copper(I) Complexes with Pyrazine and Pyrimidinyl Ancillary Ligands for White Light‐Emitting Electrochemical Cells

“…[5,[7][8][9] A wide variety of emitters has been applied to LECs, such as conjugated polymers, small molecules, and ionic transition metal complexes (iTMCs). [6,[10][11][12][13][14][15] As far as the iTMCs are concerned, efforts have recently been put toward replacing traditional Ir(III) and Ru(II)-based iTMCs by Cu(I)-counterparts (Cu-iTMCs). [11,16,17] In particular, we [18][19][20][21] and others [22][23][24][25][26] have mainly explored LECs with heteroleptic [Cu(P^P)(N^N)] + complexes, achieving efficiencies of up to 5 cd A −1 , stabilities of a few hundred hours, and luminances of a couple of hundreds cd m −2 .…”

Deep-red light-emitting electrochemical cells based on phosphor-sensitized thermally activated delayed fluorescence

“…LECs, which have great potential applications in bio-imaging, telecommunication, night-vision displays, and chemical sensing, commonly showed low device efficiencies, hindering their commercialization. In these reported studies, deep-red LECs based on phosphor-sensitized fluorescence 29,30 outperform other types of deep-red LECs, i.e., employing small molecules, [31][32][33][34][35] conjugated polymers, [36][37][38][39][40] and iTMCs. [41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57] Phosphor-sensitized fluorescence has been proven to be useful in increasing device efficiencies of fluorescent OLEDs to the levels similar to those of phosphorescent OLEDs.…”

“…21–28 However, the reported long-wavelength, i.e. , deep-red and near-infrared (NIR) LECs, which have great potential applications in bio-imaging, telecommunication, night-vision displays, and chemical sensing, commonly showed low device efficiencies, 29–61 hindering their commercialization. In these reported studies, deep-red LECs based on phosphor-sensitized fluorescence 29,30 outperform other types of deep-red LECs, i.e.…”