Fast-Switching Electrochromic Li[sup +]-Doped NiO Films by Ultrasonic Spray Deposition

Abstract

A low cost, high throughput deposition method for films of nickel oxide (NiO) and lithium-doped nickel oxide with improved electrochromic performance is demonstrated. This method is based on ultrasonic spray deposition of aqueous-based precursor solutions in air at atmospheric pressure, which represents a significant cost savings compared to vacuum deposition methods. The resultant materials are characterized by X-ray diffraction, Raman spectroscopy, electron microscopy, and electrochemical measurements. Electrochromic performance is demonstrated with in situ optical transmission measurements during electrochemical characterization. Nickel oxide materials color anodically and are thereby ideally suited to be used as counter electrode for the well-known tungsten oxide (WnormalO3) system in “smart” window applications. The coloration of nickel oxide materials is known to be slow when compared to WnormalO3 and thereby limits the overall response time of a NiO∕WnormalO3 tandem device. The analysis of potential step response data shows that our lithium-doped nickel oxide material achieves 90% of its total coloration change in 29s , which is comparable to reported measurements for WnormalO3 . These results significantly mitigate a potential bottleneck to the adoption of metal oxide electrochromic windows not only by demonstrating similar performance between NiO and WnormalO3 , but by achieving this result via low cost, highly scalable processing methods.

Cyclic voltammetry on sputter-deposited films of electrochromic Ni oxide: Power-law decay of the charge density exchange

“…The details differ, however, and the main diffraction peaks corresponding to the (111) and (220) lattice planes are shifted slightly towards higher diffraction angles for colored as well as bleached films, which implies a shrinkage of the separation between these lattice planes compared to their separation in asdeposited films. This effect is connected with the irreversible Li insertion and has been noted also in earlier work on lithiated Ni oxide [52][53][54]89]. It is associated with compressive stress whose origin is not known.…”

“…Electrochromic Ni-oxide-based films have been made also by electrophoretic deposition of Ni hydroxide nanoparticles [50] and from Ni oxide pigments deposited from water dispersion [51]. The electrochromism of binary Ni-based mixed oxides have attracted much attention during recent years, and results have been presented for such oxides containing Li [52][53][54], C [55,56], N [57], F [58], Al [59], Ti [60], V [61,62], Mn [49], Co [33], Cu [63], and W [25]. Ternary Ni-based oxides or nanocomposites containing Li-Al [64], Li-Zr [65], and Li-W [66] have given particularly interesting results.…”

Anodic Electrochromism for Energy‐Efficient Windows: Cation/Anion‐Based Surface Processes and Effects of Crystal Facets in Nickel Oxide Thin Films

“…The electrochromism of lithium-containing Ni oxide films has been investigated in numerous studies aimed at elucidating basic optical and electrochemical mechanisms [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] as well as to produce counter electrodes for application in W-oxide-based EC devices [5,27,32,[34][35][36][37][38] .…”

“…[ 4,6,7 ] In this case, optical transmittance modulation can be used to to produce counter electrodes for application in W oxide-based EC devices. [ 5,27,32,[34][35][36][37][38] We fi rst consider work by Passerini et al, [17][18][19]22,39 ] who proposed a simple two-step electrochemical reaction scheme for Li + insertion/extraction in sputter-deposited Ni oxide fi lms immersed in LiClO 4 -PC. This scheme involves an initial irreversible bleaching of the as-deposited Ni oxide by…”

Scalable synthesis of improved nanocrystalline, mesoporous tungsten oxide films with exceptional electrochromic performance

“…Moreover, the use of benign solvents such as water and alcohol allows processing to be conducted under ambient conditions. Spray pyrolysis has been demonstrated for the production of high quality transparent electrodes [18] as well a nickel oxide [19], a leading counter electrode in the electrochromic stack [2]. As such one could envision employing USD for in-line production of smart windows.…”