Smart Windows with Neutral Color, Excellent Durability, and Low Cost
using Reversible Metal Electrodeposition
November 3, 2016 Christopher Barile,
Prof. Michael McGehee, Jingye Hou, Dan Slotcavage, Tyler Hernandez, Michael Strand
versus
The Potential of Smart Windows • Dynamically control solar radiation • Buildings used 40% of U.S. electricity
in 2015 • 20% energy savings for lighting,
cooling, and heating • Car windows, sunglasses
U.S. Energy Information Administration, 2015. View Glass, Energy Savings Guide, http://viewglass.com/assets/pdfs/workplace-white-paper.pdf
SAGE Windows, Chabot College, Hayward, CA
Tinted
Transparent
Electrochromic Devices
• Materials that change color with voltage
• Transition metal oxides
x Li+ + x e- + WO3 LixWO3 colorless blue
Mortimer, R. J. Ann. Rev. Mater. Res. 2011, 41, 241.
Drawbacks of Electrochromics
• Not color neutral • Absorptive poor heat management • Expensive due to multiple layers (≥ 4) • Difficult to scale • Cycle life (need > 10,000)
WO3 Electrochromic Boeing 787 Dreamliner
Thakur, V. K. et al. Adv. Mater. 2012, 24, 4071.
Reversible Metal Electrodeposition
• Only ~20 nm metal required for complete opacity
• Reflective
M+ + e- M(window) Cathode:
Anode:
Net:
M(frame) M+ + e-
M(frame) M(window)
Anode: Metal counter electrode around glass
Cathode: Transparent conducting substrate on glass
Electrolyte containing M+
First Prototypes: M = Cu-Pb, Cu-Ag
Metal Deposition from a Cu-Pb System
-0.35 V deposition,
0 s
30 s
60 s
Visible Infrared
ITO on glass working, Pt counter, Ag/AgCl reference electrodes
Metal Deposition from a Cu-Pb System
-0.35 V deposition, +0.45 V stripping
0 s
30 s
60 s
90 s
120 s
Opaque
Transparent Transparent
Visible Infrared
Good Resting Stability ITO on glass working,
Pt counter, Ag/AgCl reference electrodes
55% Transmission 30% Transmission 5% Transmission
Morphology on Pt-modified ITO
Increasing Deposition Time
200 nm 200 nm 200 nm
Smart Window Reliability Pt-modified ITO/glass electrode
Each cycle: -0.35 V for 60 s, +0.45 V for 60 s
Maximum Transmission
Minimum Transmission
1 Cycle of Deposition:
10 Cycles of Deposition:
1000 Cycles of Deposition:
Morphology on Pt/ITO with Cycling
Reversible Electrochemical Mirror
Developing a Gel Electrolyte
Challenges: • Gel viscosity decreases ion
diffusion • Nature of Pt seed layer is
more important
Advantages: • Easier device fabrication • Less prone to leaks • Keeps electrolyte confined in
event of accident
Anchored Pt Nanoparticles
• Good uniformity obtained with anchored Pt nanoparticles for gel system
( ) ( ) n
( ) n
n
( ) n
( ) n
Towards Practical Smart Windows
• Cu-Ag gel electrolyte • Stable cycling throughout 5,500 cycles
Maximum Transmission
Minimum Transmission
10 x Speed
5 cm
Cycle 1500
10 x Speed
5 cm
Cycle 1500
Electrochromics vs. Reversible Metal
Reversible Metal Electrodeposition
Transition Metal Oxides
Light modulation Reflective (mirror or black)
Absorptive
Runnerstrom, E. L. et al. Chem. Commun. 2014, 50, 10555.
Electrochromics vs. Reversible Metal
Reversible Metal Electrodeposition
Transition Metal Oxides
Light modulation Reflective (mirror or black)
Absorptive
Color Black Blue, yellow, other
Runnerstrom, E. L. et al. Chem. Commun. 2014, 50, 10555.
Electrochromics vs. Reversible Metal
Reversible Metal Electrodeposition
Transition Metal Oxides
Light modulation Reflective (mirror or black)
Absorptive
Color Black Blue, yellow, other Switching speed Minutes Minutes
Runnerstrom, E. L. et al. Chem. Commun. 2014, 50, 10555.
Electrochromics vs. Reversible Metal
Reversible Metal Electrodeposition
Transition Metal Oxides
Light modulation Reflective (mirror or black)
Absorptive
Color Black Blue, yellow, other Switching speed Minutes Minutes Cycle life > 5,000 1,000-20,000
Runnerstrom, E. L. et al. Chem. Commun. 2014, 50, 10555.
Electrochromics vs. Reversible Metal
Reversible Metal Electrodeposition
Transition Metal Oxides
Light modulation Reflective (mirror or black)
Absorptive
Color Black Blue, yellow, other Switching speed Minutes Minutes Cycle life > 5,000 1,000-20,000 Cost Less Expensive Expensive
Runnerstrom, E. L. et al. Chem. Commun. 2014, 50, 10555.
Future Work
• Understand electrodeposit morphology • Diffuse reflection • Counter electrode design for larger windows • Cost modeling
Conclusions
• Uniform reversible metal electrodeposition • Controlled nucleation • Excellent metrics versus electrochromics • Still in early stages!
