Pulsed Driving Methods for Enhancing the Stability of Electrochemiluminescence Devices

Abstract

As a new device platform comprising only electrochemiluminescence (ECL) luminophores and an electrolyte sandwiched between electrodes, ECL devices (ECLDs) promise to be cost efficient for large-area emissive applications. However, rapid degradation of luminescence, along with thermal decomposition of the electrochemical components, has proven a seemingly fundamental problem in ECLDs. To alleviate this issue, we investigated the influence of inserting a resting period during the operation of such devices by applying a square-shaped pulsed signal. The inserted resting period enhances the device stability, as it allows the effective reaction volume near the electrodes to be replenished with ECL luminophores, thus, preventing undesired side reactions. Moreover, the application of a current pulsed signal, rather than a voltage pulse, leads to further enhancement of the device stability, attributable to even distribution of the redox reaction over the rough surface of the electrode under current control. Under controlled pulsed-current operation (100 μA at 10 Hz), the emission characteristics of an ECLD employing a neutral iridium­(III) complex as the luminophore can be preserved for ∼1 h.

Diffusion and Kinetic‐Controlled Electrochemical Reactions for Improving the Performance of Solution‐based Electrochemiluminescence Devices

“…The ECL controlled by varying the potential has attracted attention for application in various fields, such as chemical analysis, immunoassay, and optoelectronic devices . Among them, ECL devices (ECLDs) have recently been considered as promising next‐generation displays due to their low energy consumption, simple fabrication process, and ability to function in direct current (DC) and alternating current (AC) . Most ECLDs have a single active layer, in which the ECL luminophore and electrolyte are mixed between two electrodes, acting as the anode and the cathode in a sandwich‐type ECLD .…”

“…Among them, ECL devices (ECLDs) have recently been considered as promising next‐generation displays due to their low energy consumption, simple fabrication process, and ability to function in direct current (DC) and alternating current (AC) . Most ECLDs have a single active layer, in which the ECL luminophore and electrolyte are mixed between two electrodes, acting as the anode and the cathode in a sandwich‐type ECLD . Thus, the working mechanism of ECLDs differs from those of conventional light‐emitting diodes (LEDs) .…”

“…The ECL is affected both by the electron transfer rate ( k o ) between the ECL luminophore and electrode and by the diffusion‐limited reaction associated with the mass transfer of the ECL luminophore. These factors are determined by the operational method, and the type and concentration of the electrolyte . Although several studies related to this subject have been reported, the dynamics of the electrochemical reactions involving the k o and the diffusion‐limited reactions in ECLDs have not been properly elucidated.…”

“…The electrochemically stable (pq) 2 Ir(pico) acid with a high ECL quantum yield was used as the ECL luminophore . As the working mechanism of ECLDs is similar to that of bulk electrolysis in electrolytic cells, the electrolyte is a critical factor influencing the performance of ECLDs . The electrolyte affects the formation of EDLs at the electrode/active layer interface, whereby an effective potential drop occurs .…”

“…As the working mechanism of ECLDs is similar to that of bulk electrolysis in electrolytic cells, the electrolyte is a critical factor influencing the performance of ECLDs . The electrolyte affects the formation of EDLs at the electrode/active layer interface, whereby an effective potential drop occurs . Consequently, the electron transfer is facilitated by the outer‐sphere mechanism between (pq) 2 Ir(pico) and the electrode.…”