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

Abstract

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.

The Weak Microcavity as an Enabler for Bright and Fault-tolerant Light-emitting Electrochemical Cells

“…1(d) and Table 1 . From a sole charge-balance point-of-view 38 , the expected behavior is that the luminance will increase with time, since electric double layer and p-n junction formation will result in a more balanced hole/electron injection and a concomitant higher exciton formation rate. And from a sole self-absorption perspective 26 , the thinner devices should feature a higher peak luminance, as fewer photons should be lost to absorption during the passage through a thinner active layer.…”

“…It is accordingly clear that simple charge-balance 38 and self-absorption 26 arguments cannot fully explain the observed forward luminance dependency on active-layer thickness. Thus, to better understand the temporal evolution of the optoelectronic properties of operating LECs, we have systematically collected angularly and spectrally resolved intensity data.…”

Aldehyde bearing bis-cyclometalated Ir(III) complex as selective photoluminescence turn-on probe for imaging intracellular homocysteine

“…Huang and coworkers designed an iridium(III) complex which showed high specificity towards Hcy on basis of the cyclization of aldehyde with thiol [23]. Among them, iridium(III) complex has received considerable attention in the light-emitting electrochemical cells [24] and in the detection of analytes, including oxygen [25], thrombin, cocaine and K + [26], cations [27][28][29], anions [30,31], Cys [32][33][34][35], both Cys and Hcy [36][37][38][39] due to its high photoluminescent efficiencies, relatively long lifetimes and significant Stokes shifts.…”

Fully Printed Light‐Emitting Electrochemical Cells Utilizing Biocompatible Materials

“…We incorporated a 17 nm thick layer of zinc oxide (ZnO), fabricated by inkjet printing from an α‐terpineol ink. The role of ZnO is to improve the electron injection as recently reported for LECs . Although the electric double layers in the active layer account for differences in energy levels between the emitter and the electrode, an additional interlayer is necessary because the energy difference between the LUMO of super yellow and the PEDOT:PSS Fermi level is too large.…”