uu.seUppsala University Publications
Change search
Link to record
Permanent link

Direct link
BETA
Wen, Rui-Tao
Alternative names
Publications (10 of 30) Show all publications
Granqvist, C. G., Arvizu, M. A., Qu, H.-Y., Wen, R.-T. & Niklasson, G. (2019). Advances in electrochromic device technology: Multiple roads towards superior durability. Paper presented at 61st Annual Technical Conference of the Society-of-Vacuum-Coaters (SVC), MAY 05-10, 2018 , Orlando, FL, USA.. Surface & Coatings Technology, 357, 619-625
Open this publication in new window or tab >>Advances in electrochromic device technology: Multiple roads towards superior durability
Show others...
2019 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 357, p. 619-625Article in journal (Refereed) Published
Abstract [en]

Most electrochromic (EC) devices must have a service lifetime of many years, and this is particularly so for“smart windows” in buildings with good energy efficiency and indoor comfort. The central part of oxide-based EC devices contains thin films based on W oxide and Ni oxide together with an interposed electrolyte. Depending on operating conditions, these films may show degradation at a slower or faster pace, and means to prevent or reverse this phenomenon, or as a minimum allow reliable lifetime prediction, have been sought ever since the beginnings of EC technology. Here we survey recent endeavors related to EC films of W oxide and Ni oxide and show that (i) electrochemical pretreatment of films in a liquid electrolyte can significantly improve durability, (ii)electrochemical posttreatment in a liquid electrolyte can rejuvenate degraded films, (iii) mixed oxides can have better durability and optical performance than corresponding pure oxides, and (iv) lifetime prediction is possible.

Place, publisher, year, edition, pages
Elsevier, 2019
National Category
Materials Chemistry
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-369882 (URN)10.1016/j.surfcoat.2018.10.048 (DOI)000455691100083 ()
Conference
61st Annual Technical Conference of the Society-of-Vacuum-Coaters (SVC), MAY 05-10, 2018 , Orlando, FL, USA.
Funder
EU, European Research Council, 267234
Available from: 2018-12-17 Created: 2018-12-17 Last updated: 2019-02-05Bibliographically approved
Granqvist, C. G., Arvizu, M. A., Qu, H.-Y., Wen, R.-T. & Niklasson, G. (2018). Advances in electrochromic device technology: Multiple roads towards superior durability. In: Proceedings SVC: . Paper presented at Society of Vacuum Coaters 61st Annual Technical Conference, May 5-10, 2018, Orlando, FL, USA. , Article ID 9 pages.
Open this publication in new window or tab >>Advances in electrochromic device technology: Multiple roads towards superior durability
Show others...
2018 (English)In: Proceedings SVC, 2018, article id 9 pagesConference paper, Published paper (Refereed)
Abstract [en]

Most electrochromic (EC) devices must have a service lifetime of many years, and this is particularly so for “smart windows” in buildings with good energy efficiency and indoor comfort. The central part of oxide-based EC devices contains thin films based on W oxide and Ni oxide together with an interposed electrolyte. Depending on operating conditions, these films may show degradation at a slower or faster pace, and means to prevent or reverse this phenomenon, or as a minimum allow reliable lifetime prediction, have been sought ever since the beginnings of EC technology. Here we survey recent endeavors related to EC films of W oxide and Ni oxide and show that (i) electrochemical pretreatment of films in a liquid electrolyte can significantly improve durability, (ii) electrochemical posttreatment in a liquid electrolyte can rejuvenate degraded films, (iii) mixed oxides can have better durability and optical performance than corresponding pure oxides, and (iv) lifetime prediction is possible.

National Category
Materials Chemistry
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-368957 (URN)
Conference
Society of Vacuum Coaters 61st Annual Technical Conference, May 5-10, 2018, Orlando, FL, USA
Available from: 2018-12-10 Created: 2018-12-10 Last updated: 2019-03-06Bibliographically approved
Granqvist, C. G., Arvizu, M. A., Bayrak Pehlivan, I., Qu, H.-Y., Wen, R.-T. & Niklasson, G. A. (2018). Electrochromic materials and devices for energy efficiency and human comfort in buildings: A critical review. Electrochimica Acta, 259, 1170-1182
Open this publication in new window or tab >>Electrochromic materials and devices for energy efficiency and human comfort in buildings: A critical review
Show others...
2018 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 259, p. 1170-1182Article, review/survey (Refereed) Published
Abstract [en]

Electrochromic (EC) materials can be integrated in thin-film devices and used for modulating optical transmittance. The technology has recently been implemented in large-area glazing (windows and glass facades) in order to create buildings which combine energy efficiency with good indoor comfort. This critical review describes the basics of EC technology, provides a case study related to EC foils for glass lamination, and discusses a number of future aspects. Ample literature references are given with the object of providing an easy entrance to the burgeoning research field of electrochromics.

National Category
Materials Chemistry Engineering and Technology
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-350203 (URN)10.1016/j.electacta.2017.11.169 (DOI)000423968600129 ()
Available from: 2018-05-08 Created: 2018-05-08 Last updated: 2018-12-17
Wen, R.-T., Malmgren, S., Granqvist, C. G. & Niklasson, G. A. (2017). Degradation Dynamics for Electrochromic WO3 Films under Extended Charge Insertion and Extraction: Unveiling Physicochemical Mechanisms. ACS Applied Materials and Interfaces, 9(14), 12872-12877
Open this publication in new window or tab >>Degradation Dynamics for Electrochromic WO3 Films under Extended Charge Insertion and Extraction: Unveiling Physicochemical Mechanisms
2017 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 14, p. 12872-12877Article in journal (Refereed) Published
Abstract [en]

Degradation of electrochromic thin films under extended charge insertion and extraction is a technically important phenomenon for which no in-depth understanding is currently on hand. Here, we report on an explorative study of sputter-deposited WO3 films in a Li-ion-conducting electrolyte by use of cyclic voltammetry, in situ optical transmittance, and impedance spectroscopy. A cycling-dependent decrease of the charge capacity could be accurately modeled by a power-law function, and impedance spectroscopy gave evidence for anomalous diffusion as well as a higher charge transfer resistance during deintercalation than during intercalation. Thus, a consistent conceptual picture emerged for the degradation dynamics; it includes the growth of an interfacial barrier layer and also embraces anomalous diffusion coupled with dispersive power-law chemical kinetics.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2017
Keywords
WO3, thin films, electrochromism, detrapping physicochemical mechanisms
National Category
Materials Engineering Engineering and Technology
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-322183 (URN)10.1021/acsami.7b01324 (DOI)000399354100082 ()28328195 (PubMedID)
Funder
EU, FP7, Seventh Framework Programme, 267234Swedish Research Council
Available from: 2017-05-17 Created: 2017-05-17 Last updated: 2019-02-01Bibliographically approved
Niklasson, G. A., Wen, R.-T., Qu, H.-Y., Arvizu, M. A. & Granqvist, C. G. (2017). Durability of electrochromic films: Aging kinetics and rejuvenation. In: ECS Transactions: . Paper presented at 231st ECS Meeting, New Orleans, May 28 - June 1, 2017 (pp. 1659-1669). Electrochemical Society, 77
Open this publication in new window or tab >>Durability of electrochromic films: Aging kinetics and rejuvenation
Show others...
2017 (English)In: ECS Transactions, Electrochemical Society, 2017, Vol. 77, p. 1659-1669Conference paper, Published paper (Refereed)
Abstract [en]

A major challenge for energy-efficient smart window technology is to ensure the durability of electrochromic (EC) devices over aservice life of more than 20 years. In this paper, we report recent results from a fundamental study of the aging kinetics of EC tungsten oxide and nickel oxide thin films and describe electrochemical rejuvenation mechanisms that are able to restore the films to their initial state. The aging kinetics displays an approximate power-law decrease of the charge capacity as a function of cycle number. This decay of charge capacity can be understood in terms of models built on so-called dispersive chemical kinetics. Tungsten oxide and nickel oxide EC films can be rejuvenated by applying a high electrochemical potential or a small constant current. Trapped ions in the bulk or at the surface of the films can be released by these procedures.

Place, publisher, year, edition, pages
Electrochemical Society, 2017
Series
ECS Transactions ; 77 (11)
National Category
Materials Engineering
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-332945 (URN)10.1149/07711.1659ecst (DOI)000432420500151 ()
Conference
231st ECS Meeting, New Orleans, May 28 - June 1, 2017
Funder
Swedish Research Council, 2016-03713EU, European Research Council, 267234
Available from: 2017-11-02 Created: 2017-11-02 Last updated: 2018-08-30Bibliographically approved
Baloukas, B., Arvizu, M. A., Wen, R.-T., Niklasson, G. A., Granqvist, C. G., Vernhes, R., . . . Martinu, L. (2017). Galvanostatic Rejuvenation of Electrochromic WO3 Thin Films: Ion Trapping and Detrapping Observed by Optical Measurements and by Time-of-Flight Secondary Ion Mass Spectrometry. ACS Applied Materials and Interfaces, 9(20), 16996-17002
Open this publication in new window or tab >>Galvanostatic Rejuvenation of Electrochromic WO3 Thin Films: Ion Trapping and Detrapping Observed by Optical Measurements and by Time-of-Flight Secondary Ion Mass Spectrometry
Show others...
2017 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 20, p. 16996-17002Article in journal (Refereed) Published
Abstract [en]

Electrochromic (EC) smart windows are able to decrease our energy footprint while enhancing indoor comfort and convenience. However, the limited durability of these windows, as well as their cost, result in hampered market introduction. Here, we investigate thin films of the most widely studied EC material, WO3. Specifically, we combine optical measurements (using spectrophotometry in conjunction with variable-angle spectroscopic ellipsometry) with time-of-flight secondary ion mass spectrometry and atomic force microscopy. Data were taken on films in their as-deposited state, after immersion in a Li-ion-conducting electrolyte, after severe degradation by harsh voltammetric cycling and after galvanostatic rejuvenation to regain the original EC performance. Unambiguous evidence was found for the trapping and detrapping of Li ions in the films, along with a thickness increase or decrease during degradation and rejuvenation, respectively. It was discovered that (i) the trapped ions exhibited a depth gradient; (ii) following the rejuvenation procedure, a small fraction of the Li ions remained trapped in the film and gave rise to a weak short-wavelength residual absorption; and (iii) the surface roughness of the film was larger in the degraded state than in its virgin and rejuvenated states. These data provide important insights into the degradation mechanisms of EC devices and into means of achieving improved durability.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2017
Keywords
electrochromism, ellipsometry, ion trapping, smart windows, rejuvenation, time-of-flight secondary ion mass spectrometry, ToF-SIMS, WO3
National Category
Materials Chemistry Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-328716 (URN)10.1021/acsami.7b01260 (DOI)000402498600028 ()28485953 (PubMedID)
Funder
EU, FP7, Seventh Framework Programme
Available from: 2017-09-01 Created: 2017-09-01 Last updated: 2017-11-02
Wen, R.-T., Granqvist, C. G. & Niklasson, G. A. (2016). Anodic Electrochromic Nickel Oxide Thin Films: Decay of Charge Density upon Extensive Electrochemical Cycling. ChemElectroChem, 3(2), 266-275
Open this publication in new window or tab >>Anodic Electrochromic Nickel Oxide Thin Films: Decay of Charge Density upon Extensive Electrochemical Cycling
2016 (English)In: ChemElectroChem, E-ISSN 2196-0216, Vol. 3, no 2, p. 266-275Article in journal (Refereed) Published
Abstract [en]

Electrochromic (EC) Ni oxide thin films are a critical component in the smart windows. However, long-term decay of the EC performance in aprotic electrolytes is persistent and poorly understood, and it is difficult to assess lifetimes of EC devices. Here we report on charge density decline upon electrochemical cycling. The charge density decay was modeled with a power law or, alternatively, a stretched exponential; both models describe a rapid drop of charge density during the first hundreds of cycles and a subsequent slower decline. The decay is independent of film composition and applied potential range as long as the upper limit of the potential is 4.4V vs. Li/Li+. Our decay models are interpreted in terms of dispersive chemical reaction kinetics and point at ion diffusion as the rate-limiting step. Power-law exponents are consistent with diffusion. The results provide a framework for evaluating EC durability of Ni-oxide-based thin films and may be important for assessing the durability of EC devices.

Keywords
degradation kinetics, electrochromism, nickel oxide, power law, stretched exponential
National Category
Chemical Engineering
Identifiers
urn:nbn:se:uu:diva-282493 (URN)10.1002/celc.201500457 (DOI)000371254600011 ()
Funder
EU, European Research Council, 267234
Note

Correction in: Wen, R.-T., Granqvist, C. G. and Niklasson, G. A. (2016), Corrigendum: Anodic Electrochromic Nickel Oxide Thin Films: Decay of Charge Density upon Extensive Electrochemical Cycling. ChemElectroChem, 3: 675.

doi: https://doi.org/10.1002/celc.201600127

Available from: 2016-04-05 Created: 2016-04-05 Last updated: 2018-08-30Bibliographically approved
Wen, R.-T., Niklasson, G. A. & Granqvist, C.-G. (2016). Electrochromic Iridium-Containing Nickel Oxide Films with Excellent Electrochemical Cycling Performance. Journal of the Electrochemical Society, 163(2), E7-E13
Open this publication in new window or tab >>Electrochromic Iridium-Containing Nickel Oxide Films with Excellent Electrochemical Cycling Performance
2016 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 163, no 2, p. E7-E13Article in journal (Refereed) Published
Abstract [en]

Electrochromic Ni oxide thin films attract much interest because of their large potential for applications as optically active layers in energy-saving and comfort enhancing smart windows in buildings. However Ni oxide, typically being the anodic counter electrode in a W-oxide-based device, may suffer severe charge capacity degradation upon extended electrochemical cycling. It is therefore important to identify improved Ni-oxide-based thin films for electrochromics. Here we describe a new class of such films wherein an addition of a small amount of Ir to Ni oxide is found to provide strongly improved electrochemical cycling durability. Best properties were achieved with Ir/(Ir + Ni) = 7.6%, and such films displayed charge capacity and optical modulation that, remarkably, were still increasing after 10,000 cycles.

Keywords
Electrochromic, Ir -Ni oxide, thin films, durability
National Category
Chemical Sciences Physical Sciences Engineering and Technology Materials Chemistry
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-267706 (URN)10.1149/2.0591602jes (DOI)000367324400057 ()
Funder
EU, European Research Council, 267234
Available from: 2015-11-25 Created: 2015-11-25 Last updated: 2018-08-30Bibliographically approved
Wen, R., Arvizu, M. A., Niklasson, G. A. & Granqvist, C.-G. (2016). Electrochromics for energy efficient buildings: Towards long-term durability and materials rejuvenation. Paper presented at 58th Annual Technical Conference of the Society-of-Vacuum-Coaters (SVC), APR 25-30, 2015, Santa Clara, CA. Surface & Coatings Technology, 290, 135-139
Open this publication in new window or tab >>Electrochromics for energy efficient buildings: Towards long-term durability and materials rejuvenation
2016 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 290, p. 135-139Article in journal (Refereed) Published
Abstract [en]

Electrochromic devices such as "smart windows" for energy efficient windows must be durable enough for many years of practical use. Typical devices employ films based on W oxide and Ni oxide, and this paper surveys recent progress on durability-related issues for these materials. In the case of W oxide, we discuss the beneficial effects of Ti addition, and we describe recent and unexpected progress concerning galvanostatic rejuvenation of aged W oxide films. For Ni oxide, we report how charge exchange declination during extended voltammetric cycling can be modeled in terms of a power law.

Keywords
Electrochromics, Energy efficient buildings, Durability, Rejuvenation
National Category
Other Physics Topics Engineering and Technology
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-297549 (URN)10.1016/j.surfcoat.2016.02.031 (DOI)000374370600021 ()
Conference
58th Annual Technical Conference of the Society-of-Vacuum-Coaters (SVC), APR 25-30, 2015, Santa Clara, CA
Available from: 2016-06-27 Created: 2016-06-23 Last updated: 2018-08-30
Wen, R.-T., Niklasson, G. A. & Granqvist, C. G. (2016). Eliminating Electrochromic Degradation in Amorphous TiO2 through Li-Ion Detrapping. ACS Applied Materials and Interfaces, 8(9), 5777-5782
Open this publication in new window or tab >>Eliminating Electrochromic Degradation in Amorphous TiO2 through Li-Ion Detrapping
2016 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 8, no 9, p. 5777-5782Article in journal (Refereed) Published
Abstract [en]

The quest for superior and low-cost electroehromic (EC) thin films, for applications in smart windows, remains strong because of their large importance for energy-efficient buildings. Although the development of new EC materials for improved devices is important, diminishing or reversing degradation is another key issue, and electrical rejuvenation of degraded EC materials can offer new opportunities. Here we demonstrate that cathodically coloring EC thin films of TiO2, which normally suffer from ion-trapping-induced degradation of charge capacity and optical modulation upon extensive electrochemical cycling, can recover their initial EC performance by a rejuvenation procedure involving Li+ ion detrapping. Thus, the initial performance can be regained, and refreshed TiO2 films exhibit the same degradation features as as-deposited films upon prolonged electrochemical cycling. The rejuvenation was carried out by using either galvanostatic or potentiostatic treatments. Our study may open avenues to explore the recovery not only of EC materials and devices based on those but also for other ion-exchange-based devices.

Place, publisher, year, edition, pages
ACS: , 2016
Keywords
smart windows, TiO2, electrochromism, ion-trapping, rejuvenation
National Category
Nano Technology Condensed Matter Physics
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-283772 (URN)10.1021/acsami.6b00457 (DOI)000371945700007 ()26910644 (PubMedID)
Funder
EU, FP7, Seventh Framework Programme, 267234
Available from: 2016-04-14 Created: 2016-04-14 Last updated: 2018-08-30Bibliographically approved
Organisations

Search in DiVA

Show all publications