WO₃‐Based Electrochromic Distributed Bragg Reflector: Toward Electrically Tunable Microcavity Luminescent Device

Abstract

with various refractive indices are critical components in optical feedback systems for lasers [4] and also play an important role in high-performance light-emitting devices, [5,6] photodetectors, [7] and solar cells. [8,9] The optical properties of such systems can be precisely tailored by manipulating the chemical composition and architecture (thickness and porosity) of stacked layers. Recently, special research interests lie in responsive DBRs, in which dynamical changes of the optical properties (reflectivity, band-gap, structural color) in response to external stimuli (such as light, temperature, chemical species, and electrical field) have been demonstrated. [10][11][12][13] Among them, electrical field is the most easily controlled stimulus and simplifies integration into existing electronic components, finding new applications in active filters, tunable laser sources, and color manipulation for optical communication and display technologies.In this regard, redox-active polymers, [14][15][16] polyelectrolyte hydrogels, [17,18] liquid crystals, [19,20] or electrochromic materials [21,22] have been introduced into the periodic structure for realizing electrically tuned optical coatings. The shape and size manipulation using redox-active polymers, polyelectrolyte hydrogel, and liquid crystal usually cause large reflectance shifts, but slow response and poor durability, unsuitable for practical applications. By comparison, electrochromic materials can reversibly change their electronic structure and optical property (transmittance, reflectance, or absorption) under a small driving voltage and have been widely applied in energysaving smart windows, switchable mirrors, and displays. [23][24][25][26] This color change is mainly caused by the adjustable absorption as well as change of refractive index. Moreover, electrochormic materials have unique open-circuit memory effect (bistability in colored and bleached states), making it possible to prepare devices with low energy consumption and good stability. [27] DBRs employ two kinds of electrochromic materials with different refractive indices such as WO 3 and NiO and have shown electrically tunable reflectivity and photonic stop-band. [22] However, the preparation process was relatively complex with the requirement for high-temperature calcination at 450 C after depositing of each layer. In addition, complementary coloration effects of WO 3 (cathodic coloration) and NiO (anodic coloration)The electroresponsive WO 3 -based electrochromic distributed Bragg reflectors (ECDBRs) are fabricated by means of one-step, room temperature glancingangle electron-beam evaporation. The reflectance and Bragg wavelength of ECDBRs can be precisely and reversibly tailored on a large scale by simply applying a small bias voltage (±1.1 V) due to the electrochromic effect of the WO 3 layer, and this unique character is utilized to construct an electrically tunable microcavity luminescent device with embedded green CdSe@ZnS quantum dots (QDs). Therefore, large and reversible modulation i...

Ordered Hybrid Micro/Nanostructures and Their Optical Applications

“…Thus, the colorimetric sensor of voltage is obtained. Based on the same mechanism, some inorganic substances including WO 3 , NiO, are also applied as building blocks of structures to fabricate electricity actuating sensor . 2) The surrounding ion environment changes.…”

Electro-responsivity in electrolyte-free and solution processed Bragg stacks

“…24,[35][36][37][38] However, most of the recent works in the field of electrochromic Bragg mirrors (ECBM) rely on the use of liquid electrolytes that can pose issues in terms of chemical and environmental stability. 5,[42][43][44] Among the various degrees of freedom to be exploited to engineer the PhC's optical response, electrochemical doping of plasmonic materials represents a promising approach to modulate the refractive index contrast and, hence, the structural colour without the need to replace the constituent media. 39 For this purpose, the use of heavily doped metal oxide nanoparticles with plasmonic response in the near infrared (NIR) part of the spectrum is of great interest, since the sensibly lower carrier density in these materials compared with classical bulk metals (10 21 cm -3 vs. 10 23 cm -3 ) 40,41 allows for a fine control over their dielectric function by means of electro-optical doping.…”

“…39 For this purpose, the use of heavily doped metal oxide nanoparticles with plasmonic response in the near infrared (NIR) part of the spectrum is of great interest, since the sensibly lower carrier density in these materials compared with classical bulk metals (10 21 cm -3 vs. 10 23 cm -3 ) 40,41 allows for a fine control over their dielectric function by means of electro-optical doping. 5,38,[42][43][44] In this work, we integrate a doped metal oxide widely employed in optoelectronics as transparent electrode namely indium tin oxide (ITO), in a fully solution-processed 1D PhC structure made of alternating layers of ITO and TiO2 nanoparticles. Interestingly, we observe that the tunable optical response of ITO's NIR plasmon resonance via electro-doping , can be translated easily into the visible region thanks to their integration into a photonic structure and the thus obtained modulation of the photonic bandgap.…”

A Multi‐Stimuli‐Responsive Oxazine Molecular Switch: A Strategy for the Design of Electrochromic Materials

“…Electrochromic materials (ECM), characterized by at unable color switched by an electrical field, [1,2] have attracted much attention in the past few decades duet ot heir wide application potential, [3] such as in smart windows, [4][5][6][7] auto rearview mirrors, reflectived isplays, [8][9][10] and so on. [1,11] At present,m etal oxides (WO 3 ), [5,11] conducting polymers, [12][13][14] and viologen derivatives [15] are the three most intensively researched types of ECM.…”