Enhanced Luminance of Electrochemical Cells with a Rationally Designed Ionic Iridium Complex and an Ionic Additive

Abstract

Light-emitting electrochemical cells (LEECs) offer the potential for high efficiency operation from an inexpensive device. However, long turn-on times and low luminance under steady-state operation are longstanding LEEC issues. Here, we present a single-layer LEEC with a custom-designed iridium(III) complex and a lithium salt additive for enhanced device performance. These devices display reduced response times, modest lifetimes, and peak luminances as high as 5500 cd/m(2), 80% higher than a comparable device from an unoptimized complex and 50% higher than the salt-free device. Improved device efficiency suggests that salt addition balances space charge effects at the interfaces. Extrapolation suggests favorable half-lives of 120 ± 10 h at 1000 cd/m(2) and 3800 ± 400 h at 100 cd/m(2). Overall, complex design and device engineering produce competitive LEECs from simple, single-layer architectures.

Impact of the use of sterically congested Ir(iii) complexes on the performance of light-emitting electrochemical cells

“…The related complex [Ir(dPhPy) 2 (bpy)]PF 6 , R3 (where dPhPy is 2,4diphenylpyridine and bpy is 2,2ʹ-bipyridine) bears a phenyl group on the 4-position of the pyridine of the C^N ligand in lieu of a mesityl group and contains a bpy N^N ligand in lieu of the dtBubpy ligand. 9 In CH 2 Cl 2 , complex R3 exhibits yellow phosphorescence (l em = 598 nm) with a F PL of 21% . A single-layer LEEC based on R3 containing a lithium salt additive showed improved device performance compared to the unsubstituted analogue.…”

Bright and Effectual Perovskite Light-Emitting Electrochemical Cells Leveraging Ionic Additives

“…To satisfy the other requirements, we introduce LiPF6 salt, a salt that we have previously used to attain high performance in LECs utilizing ionic transition metal complexes. [16][17][18] We prepared films with an optimal concentration of the polymer electrolyte poly(ethylene oxide) (PEO) and systematically studied the effect of LiPF6 salt addition.…”

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“…[5,6] For example, for [Ir(ppy) 2 (bpy)] + (Hppy = 2-phenylpyridine, bpy = 2,2'-bipyridine) type complexes,d ifferent emission colors, photoluminescence quantum yields (PLQY), and device performances have been obtained upon modification of the cyclometallating Hppy or the ancillary bpy ligands. [5,6] Whereas iridium-based emitters can be extremely efficient, [7][8][9] their replacement with copper-based compounds has the advantage of higher abundance and therefore the markedlyl ower price of copper compared to iridium, which also translates to the resulting costs of the devices. [10] Furthermore, many copperc omplexes are provent oe xhibit thermally activatedd elayed fluorescence (TADF), am echanism which allows the thermal population of the energetically highers inglet excited state from the triplet excited state.…”