Electrochromic properties of Al doped B-substituted NiO films prepared by sol–gel
Xianchun Lou
,Xiujian Zhao, Jiamin Feng
Key Laboratory of Silicate Materials Science and Engineering (Wuhan University of
Technology), Ministry of Education, 122 Luoshi Road, Hongshan District, Wuhan, Hubei 430070, PR China.
Introduction
Results and Discussion
Conclusions
zhaoxj@public.wh.hb.cn
XRD patterns
20 30 40 50 60 70 80
¡ ó
¡ ó ¡ ó ¡ ó ¨ ‹
¨ ‹
¨ ‹
2 Theta ( O )
intensity (arbitrary unit)
¡ ó NiO
¨ ‹ Ni
0.0 0.1 0.2 0.3
4 8 12 16 20
Average Crystallite size (nm)
Al Content (Al/Ni)
Treated powder with different B content
The crystalline size of B
xtreated at 400
oC
Abstract
200 400 600 800 1000 1200
0 20 40 60
80 A3
A2 A1
transmittance (%)
Wavelength (nm) A0
colored state
400 600 800 1000 1200
50 60 70 80 90
A2 A3 A1
transmittance (%)
wavelength (nm) A0
bleached state
Tranmittance
Bleached state Colored state
-1 .0 -0 .5 0 .0 0 .5 1 .0 1 .5
-0.00 30 -0.00 15 0.0 0 00 0.0 0 15 0.0 0 30 0.0 0 45
2 0 0 1 5 0
1 0 0 5 0 Current (A/cm2)
V o lta g e (V ) 1 A0
-1.0 -0 .5 0.0 0.5 1 .0 1.5
-0.0010 -0.0005 0.0000 0.0005 0.0010 0.0015
Current (A/cm2)
v o ltag e (V ) A2
Cyclic coltammograms
B
0film B
2film
HRTEM of B
2film
Bleached state Colored state
In this paper Al doped B-substituted NiO films were prepared by sol-gel method. The effects of Al content on the electrochromic (EC) properties and durability of the AlXB0.15NiO films were studied with X-ray diffraction (XRD), transmission electron microscopy (TEM). The electrochemical and electrochromic properties were examined by cyclic voltammetric (CV) measurements and UV-Vis spectrophotometer, respectively. Al-doped could prevent the crystallization of the films, which exhibited much better electrochemical and electrochromic properties than undoped samples. The bleached-state absorptance could be significantly lowered when the aluminum (a type known to form oxides with large optical band gaps) added. Electrochromic efficiencies measured at λ=500 nm of films with different Al-doped reach ~30 cm2C- 1, w ith a variat ion in transmittance u p to 70%
Electrochromic (EC) materials have being extensively studied by many authors in order to develop high-efficiency, low cost and durable devices that can be used in large area surfaces. Nickel oxides thin films are well suitable for device operations in conjunction with tungsten oxide thin films.
Among various mixed oxides, we identified the B2O3-NiO system as showing better electrochromic properties than NiO thin films when cycled in KOH liquid electrolyte.
However, the films have lower transmittance of the bleached state. In the present work, we have synthesized the B-NiO and Al, B-doped NiO films by sol-gel process. The effect of Al content on the structure, optical and electrochromic properties of (Al)-BNiO xerogels and films was studied.
Experimental
The precursor solution was prepared by dissolving nickel acetate powder into 2-methoxyethanol and monoethanolamine mixture at room temperature. The molar ratio of monoethanolamine to nickel acetate was kept at 1.0 with the concentration of nickel acetate in the precursor solution being of 0.5 mol/l. Different amounts of aluminum nitrate and boracic acid dissolved in elthanol and then added to the Ni solution to obtain different Alx/B0.15-Ni solution. Double NiO-based films were deposited on ITO glass by the dip coating technique. The coated film was then sintered at 400 oC for 1h in air. The thin films were characterized by XRD, T E M , U V - V i s - N I R s p e c t r o p h o t o m e t e r a n d C V .
In this paper Al doped B-substituted NiO films were prepared by sol-gel method. The effects of Al content on the electrochromic (EC) properties and durability of the AlXB0.15NiO films were studied. Al-doped could prevent the crystallization of the films, which exhibited much better electrochemical and EC properties than undoped samples. The bleached-state absorptance could be significantly lowered when the aluminum (a type known to form oxides with large optical band gaps) added. The presence of Al was associated with a limited dissolution of the oxidized phases and stabilized the transition of between α-phase Ni(OH)2and γ-NiOOH, which reduce the volume change during the CV cycles. Electrochromic efficiencies measured at λ=550 nm of films for A2 reach ~30 cm2C-1, with a variation in transmittance up to 70~80%.
