High-Performance Electrofluorochromic Switching Devices Using a Novel Arylamine-Fluorene Redox-Active Fluorophore

Abstract

Fluorescent light modulation by small electric potentials has gained huge interest in the past few years. This phenomenon, called electrofluorochromism, is of the utmost importance for applications in optoelectronic devices. Huge efforts are being addressed to developing electrofluorochromic systems with improved performances. One of the most critical issue is their low cyclability, which hampers their widespread use. It mostly depends on the intrinsic reversibility of the electroactive/fluorophore molecular system and on device architecture. Here we show a novel fluorene-based mixed-valence electrofluorochromic system that allows direct electrofluorochromic switching and exhibits incomparable electrochemical reversibility and device cyclability of more than 10 000 cycles.

Overview on the Recent Progress on Electrofluorochromic Materials and Devices: A Critical Synopsis

“…www.advopticalmat.de of the ethylviologen occurs. [33] In this potential range, CR up to 40 are obtained corresponding to more than 90% of the photoluminescence quenching, (t ON = 60 s above 1.5 V; Table 1). In order to further evaluate the EFC performances of the devices a series of alternating ON and OFF pulses with different duration and voltage intensity were applied.…”

“…This issue has been recently investigated by our group, with a series of TPA-π-TPA structures with fluorene-based π-conjugated spacers of different length, all exhibiting very high photoluminescence quantum yields (up to 92%). [33,[83][84][85][86] Typically, coupled arylamine-mixed valence compounds (those belonging to classes II and III of Robin and Day [87,88] ) show a large potential splitting (>100 mV, under different medium polarity and ion pairing conditions), [89,90] that is the difference between the first and the second oxidation potentials ( 2 1 Figure 6). The electron coupling, which contributes to the splitting to a significant extent in strongly coupled systems, decreases as the length of the π-bridge increases ( Figure 6).…”

“…This electroluminochromic effect is important and can be used to control the color of the emitted light, too. [19,62,92] The exceptional properties of compound I have been exploited in all-in-one single layer devices, [33] where the electrofluorochromic layer was formed by polymer gels incorporating different amounts of the mixed valence compound, where the C 6 H 13 chains are replaced with the C 5 H 11 O 2 chains (1% to 10% (w/w)), as anodic component and ethylviologen perchlorate as cathodic one. The EFC MV IV in the gel preserves its high photoluminescence quantum yield (63%) by restriction of the intramolecular motions in the more viscous device environment, despite its concentration ranged from (10 −3 -10 −2 m), thus no significant ACQ occurs.…”

“…Adapted with permission. [33] Copyright 2019, American Chemical Society. radical cation and no side reaction occurs.…”

“…[25][26][27] However, we are going to show that, besides some excellent reviews [22,28,29] published early in the last decade, there was a significant number of scientific articles published in the last few years, demonstrating the increasing interest on electrofluorochromism, both from a technological evolution point of view and from the academic ones. All these publications are mainly focused on EFC materials development [30][31][32][33][34][35][36] (i.e., organic, inorganic, hybrid-based, small molecules or polymer-based), highlighting, on the other hand, the lack of a significant development of the related EFC devices and applications. Another critical issue in this field is the quantitative evaluation of the materials/devices performances.…”