Electrochromic smart windows offer a viable route to reducing the consumption of buildings energy, which represents about 30% of the worldwide energy consumption. Smart windows are far more compelling than current static windows in that they can dynamically modulate the solar spectrum depending on climate and lighting conditions or simply to meet personal preferences. The latest generation of smart windows relies on nominally transparent metal oxide nanocrystal materials whose chromism can be electrochemically controlled using the plasmonic effect. Plasmonic electrochromic materials selectively control the near infrared (NIR) region of the solar spectrum, responsible for solar heat, without affecting the visible transparency. This is in contrast to conventional electrochromic materials which block both the visible and NIR and thus enables electrochromic devices to reduce the energy consumption of a building or a greenhouse in warm climate regions due to enhancements of both visible lighting and heat blocking. Despite this edge, this technology can benefit from important developments, including low-cost solution-based manufacturing on flexible substrates while maintaining durability and coloration efficiency, demonstration of independent control in the NIR and visible spectra, and demonstration of self-powering capabilities. This thesis is focused on developing low-temperature and all-solution processed plasmonic electrochromic devices and dual-band electrochromic devices. We demonstrate new device fabrication approaches in terms of materials and processes which enhance electrochromic performance all the while maintaining low processing temperatures. Scalable fabrication methods are used to highlight compatibility with high throughput, continuous roll-to-roll fabrication on flexible substrates. In addition, a dualband plasmonic electrochromic device was developed by combining the plasmonic layer with a conventional electrochromic ion storage layer. This enables independent control of the transmittance of NIR and visible spectra and is done without time- and energyintensive synthesis and processing methods. We have fabricated self-powered smart windows by integrating the plasmonic and dual-band devices with organic photovoltaic mini-modules and introduced static color bias with the help of photonic crystals to explore a few possibilities of multi-platform building integration.

The building sector is one of the sectors that consume most energy in Sweden. Sweden aims thereby to reduce energy use in buildings by 20% by 2020 and 50% by 2050. To achieve these goals, more energyefficient buildings must be produced, and more energy-efficient measures must be implemented on existing buildings. Electrochromic windows are claimed to reduce the need for heating and cooling, as well as the need for artificial lighting. However, there is limited research on smart windows in the Nordic climate.   This thesis examines electrochromic windows in Sweden, using the IDA ICE 4.7.1 simulation program. The study includes a comparative analysis of an office building model with conventional windows and motorized awnings, versus electrochromic windows with different control strategies, to investigate the building’s impact. In total, eight different scenarios are simulated in Stockholm, Umeå and Malmö. The electrochromic window scenarios consist of control algorithms where the windows are always on or off, as well as algorithms that respond to sunlight, daylight, operative temperature or scheduling. The conventional windows and awnings scenario represents the reference building. The Swedish building certification system "Miljöbyggnad" is used as a guideline for evaluating energy use, heating power demand, solar heat load, thermal climate, and daylight.   The results show that electrochromic windows have little impact on the building. None of the scenarios succeed in obtaining higher certification than BRONZE, which corresponds to the authority's requirements for newly built buildings. However, electrochromic windows have a significant effect on the solar heat load and the lux level in the building, but unfortunately not enough to get a better building grade. There is no remarkable difference between the indicators and scenarios. Furthermore, the results show that scenarios that are shaded often (Always on, Daylight Control, Solar Control strategy) achieve GOLD ratings in solar heat load, but have the least impact on energy consumption and vice versa. Always off, Operative Temperature Control, and Schedule, Façade and Window strategy upgrades by one level in energy use. This confirm previous studies that claim that electrochromic windows have the greatest potential in energy saving in hot climate. This explains why there is hardly any difference between scenarios and cities.   The thesis lacks specific costs for electrochromic windows. Thus, the cost estimate is based on generalizations and assumptions, in which the cheapest and most expensive options are investigated. If the building has well-functioning windows and awnings, it is not cost effective to switch to electrochromic windows, since the payback time is far too long. But if the building was between conventional windows and electrochromic windows during the planning phase, it might be interesting to conduct a detailed cost analysis. According to this study, the Operative Temperature Control strategy saves approximately 6 333kr during the simulation period. The cost differences between conventional windows with motorized awnings, and the cheapest version of electrochromic windows is around 60 000kr. This would provide a refund within 10 years, given that energy prices, energy consumption and currency value are the same. After that, the window would cut the energy costs in the form of saved energy.   However, the study concludes that electrochromic windows are not necessary in this project from a Miljöbyggnad perspective, since the building grade remains the same and the economic gain is uncertain. / Byggnadssektorn är en av de sektorer som använder mest energi i Sverige. Därmed har Sverige som mål att minska energianvändningen i byggnader med 20% år 2020, och 50% år 2050. För att uppnå dessa mål måste fler energieffektiva byggnader produceras, samt fler energieffektiva åtgärder måste genomföras på befintliga byggnader. Elektrokroma fönster hävdas minska behovet av uppvärmning och kylning, samt behovet av artificiell belysning. Det finns dock begränsad forskning om smarta fönster i det nordiska klimatet.   Detta examensarbete undersöker elektrokroma fönster i Sverige, med hjälp av simuleringsprogrammet IDA ICE 4.7.1. Arbetet omfattar en jämförande analys av en kontorsbyggnadsmodell med vanliga fönster och motoriserade markiser, kontra elektrokroma fönster med olika kontrollstrategier, för att undersöka byggnadens påverkan. Sammanlagt simuleras åtta olika scenarier i Stockholm, Umeå och Malmö. De scenarier med elektrokroma fönster består följaktligen av kontroll algoritmer där fönsterna är alltid på eller avstängda, samt algoritmer som reagerar på solljus, dagsljus, operativa temperatur eller schemaläggning. Scenariot med vanliga fönster och markiser representerar referensbyggnaden. Det svenska byggnadscertifieringssystem ”Miljöbyggnad” används som riktlinje för evaluering av energianvändning, värmeeffektbehov, solvärmelast, termiskt klimat, och dagsljus. Resultaten visar att elektrokroma fönster har liten påverkan på byggnaden. Ingen av scenarierna lyckas få högre certifiering än BRONS, vilket motsvarar myndighetens krav på nybyggda byggnader. Dock så har elektrokroma fönster signifikant inverkan på solvärmelasten och lux nivån i byggnaden, men tyvärr inte tillräckligt för att få ett bättre byggnads betyg. Det är ingen anmärkningsvärd skillnad sinsemellan indikatorerna och scenarierna. Vidare visar resultaten att scenarier som är skuggade ofta (Alltid på-, Dagljuskontroll-, Solljuskontrollstrategin) uppnår GULD betyg inom solvärmelast men har minst inverkan på energiförbrukningen och vice versa, Alltid av-, operativa temperaturkontroll, samt schemaläggning, fasad och fönster strategin uppgraderas ett steg inom energianvändning. Detta styrker tidigare studier som påstår att elektrokroma fönster har störst potential i energibesparing i varma klimat.   Detta förklarar den minimala skillnaden av byggnadens påverkan mellan städer och scenarier. I denna rapport saknas specifika kostnader för elektrokroma fönster. Därmed baseras kostnadsuppskattningen på generaliseringar och antagande, där billigaste och dyraste alternativet undersökts. Om byggnaden har väl fungerande fönster och markiser, är det inte kostnadseffektiv att byta till elektrokroma fönster, då återbetalningstiden är alldeles för lång. Men om byggnaden stod mellan vanliga fönster och elektrokroma fönster i planeringsfasen kan det vara intressant att göra en noggrann analys. Enligt denna studie så sparar den Operativa Temperatur strategin ca. 6 333kr per år. Det skiljer ca 60 000kr mellan vanliga fönster med markiser, och elektrokroma fönster. Detta skulle ge en återbetalning inom 10 år förutsatt att energipriserna, energiförbrukningen samt valuta värdet är desamma. Därefter skulle fönstret minska utgifterna i form av sparad energi.   Slutsatsen är dock att elektrokroma fönster inte är nödvändiga i detta projektet från en Miljöbyggnads synpunkt, eftersom att det inte förbättrar byggnadsbetyget. Dessutom kvarstår osäkerheten med kostnader.

abstract: ABSTRACT Autonomous smart windows may be integrated with a stack of active components, such as electrochromic devices, to modulate the opacity/transparency by an applied voltage. Here, we describe the processing and performance of two classes of visibly-transparent photovoltaic materials, namely inorganic (ZnO thin film) and fully organic (PCDTBT:PC70BM), for integration with electrochromic stacks. Sputtered ZnO (2% Mn) films on ITO, with transparency in the visible range, were used to fabricate metal-semiconductor (MS), metal-insulator-semiconductor (MIS), and p-i-n heterojunction devices, and their photovoltaic conversion under ultraviolet (UV) illumination was evaluated with and without oxygen plasma-treated surface electrodes (Au, Ag, Al, and Ti/Ag). The MS Schottky parameters were fitted against the generalized Bardeen model to obtain the density of interface states (Dit ≈ 8.0×1011 eV−1cm−2) and neutral level (Eo ≈ -5.2 eV). These devices exhibited photoconductive behavior at λ = 365 nm, and low-noise Ag-ZnO detectors exhibited responsivity (R) and photoconductive gain (G) of 1.93×10−4 A/W and 6.57×10−4, respectively. Confirmed via matched-pair analysis, post-metallization, oxygen plasma treatment of Ag and Ti/Ag electrodes resulted in increased Schottky barrier heights, which maximized with a 2 nm SiO2 electron blocking layer (EBL), coupled with the suppression of recombination at the metal/semiconductor interface and blocking of majority carriers. For interdigitated devices under monochromatic UV-C illumination, the open-circuit voltage (Voc) was 1.2 V and short circuit current density (Jsc), due to minority carrier tunneling, was 0.68 mA/cm2. A fully organic bulk heterojunction photovoltaic device, composed of poly[N-9’-heptadecanyl-2,7-carbazole-alt-5,5-(4’,7’-di-2-thienyli2’,1’,3’-benzothiadiazole)]:phenyl-C71-butyric-acidmethyl (PCDTBT:PC70BM), with corresponding electron and hole transport layers, i.e., LiF with Al contact and conducting/non-conducting (nc) PEDOT:PSS (with ITO/PET or Ag nanowire/PDMS contacts; the illuminating side), respectively, was developed. The PCDTBT/PC70BM/PEDOT:PSS(nc)/ITO/PET stack exhibited the highest performance: power conversion efficiency (PCE) ≈ 3%, Voc = 0.9V, and Jsc ≈ 10-15 mA/cm2. These stacks exhibited high visible range transparency, and provided the requisite power for a switchable electrochromic stack having an inkjet-printed, optically-active layer of tungsten trioxide (WO3), peroxo-tungstic acid dihydrate, and titania (TiO2) nano-particle-based blend. The electrochromic stacks (i.e., PET/ITO/LiClO4/WO3 on ITO/PET and Ag nanowire/PDMS substrates) exhibited optical switching under external bias from the PV stack (or an electrical outlet), with 7 s coloration time, 8 s bleaching time, and 0.36-0.75 optical modulation at λ = 525 nm. The devices were paired using an Internet of Things controller that enabled wireless switching. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2018

Les matériaux électrochromiques organiques ont été un domaine de recherche novateur au cours des dernières décennies. Ces composés qui répondent à un potentiel appliqué par un changement de couleur sont dits électrochromes. Leur intérêt est principalement dû à leur synthèse facile, à haut rendement et à leur aspect écologique par rapport à leurs homologues inorganiques. En règle générale, ces composés ne changent de couleur qu’avec un potentiel appliqué. Développer des composés qui changent à la fois leur couleur et leur fluorescence avec un potentiel appliqué pour une utilisation dans des dispositifs électrofluorescents reste un défi majeur. Dans cette étude, une série de composés contenant de la triphénylamine (TPA) et du benzothiadiazole (BZT) ont été évalués. Ils ont été couplés à différents groupes terminaux pour moduler les propriétés photophysiques et électrochimiques. Ces composés ont été entièrement caractérisés par spectroscopie d'absorption, spectroscopie de fluorescence, voltammétrie cyclique, spectroélectrochimie et diffraction des rayons X. Cela nous a permis d'examiner l'influence de leur structure sur les propriétés. Cela nous a également permis d'identifier les composés d'intérêt idéaux pour une utilisation dans des appareils fonctionnels. Les dispositifs contenant du TPA et du BZT sont idéalement employée pour la fabrication de « fenêtre intelligente ». Cela est dû à l'activité électrochimique du TPA ainsi qu'à la fluorescence à l'état solide du noyau BZT. Pour améliorer encore les propriétés des dispositifs, un système passif était le but ultime. Cela contraste avec les dispositifs actifs où un potentiel doit être appliqué en continu pour que la couleur induite soit cohérente. Dans ce but, des couches cathodiques ont été préparées et étudiées dans un dispositif et leur utilisation comme réservoir d'ions dans un dispositif électrochromique / électrofluorescent passif a été testée. Les résultats préliminaires ont montré que les dérivés d'anthraquinone avaient des propriétés idéales pour les couches cathodiques. / Organic electrochromic materials have been a hot area of research during the past decades. These compounds that respond to an applied potential with a color change are said to be electrochromic. Their interest is mainly because of the easy synthesis, convenient mass production, and eco-friendly preparation compared to their inorganic counterparts. Typically, these compounds change only their color with an applied potential. To develop compounds that change both their color and their fluorescence with a potential applied for use in electrofluorescent devices remains a major challenge. In this study, a series of compounds containing triphenylamine (TPA) and benzothiadiazole (BZT) were evaluated. They were coupled with different end groups to tune the photophysical and electrochemical properties. These compounds were fully characterized by absorption spectroscopy, fluorescence spectroscopy, cyclic voltammetry, spectroelectrochemistry, and X-ray diffraction along with other techniques. This allowed us to examine the influence of their structure on the properties. It also allowed us to identify the ideal compounds of interest for use in functioning devices. The devices containing TPA and BZT are ideally ‘smart window’ applications. This is due to the electrochemical activity by TPA as well as the solid state fluorescence of the BZT core. To further improve the properties of devices, a passive device was the ultimate goal. This is in contrast to active devices where a potential must be applied continuously for the induced color to be consistent. Towards this goal, cathodic layers were prepared and investigated in a device and their use as an ion reservoir in a passive electrochromic / electrofluorescent device was tested. Preliminary results, showed that anthraquinone derivatives had ideal properties for the cathodic layers.

The European Union (EU) has expressed determination of reducing its energy consumption and the EU’s 2010 Energy Performance of Buildings Directive states that all new buildings must be nearly zero energy by the end of the year 2020. Dynamic or “smart” windows have been shown to be able to reduce HVAC energy consumption, lighting energy and peek cooling loads in hot climates in the US but it is difficult to find any work concerned with colder climates. This study is intended to capture the performance of dynamic windows in a variety of European climates to explore potential contributions to reaching the EU’s energy goals. The building energy simulations of this study have been conducted in IDA ICE for an office section with a large window. Three model variants are compared: without a window shading, with an external window blind and with a dynamic window. This comparison is repeated for six different locations; Kiruna, Reykjavik, Stockholm, Copenhagen, Paris and Madrid. The results of this study show that the dynamic window can reduce the total consumed energy for lighting, heating and cooling in the range of 10%-30% more than the external blind, depending on location. The reduction is 50%-75% when compared to the unshaded window. This level of performance can move Europe a step closer to zero energy buildings.

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<p>Smart windows that modulate solar radiation by changing their optical state in response to temperature stimulus are developing as promising solutions towards reducing the energy consumption of buildings. The market adoption of such systems has been slow due to the barriers in scalability, cost, as well as complexity in their integration into existing systems. Aiming these features, we have proposed a retrofit smart window design based on the temperature-responsive polymer Methyl Cellulose (MC). The system utilizes a sustainable, earth abundant and cost-effective cellulose based thermo-responsive material to transform existing windows to a thermally dynamic smart window system. The observed optical change of MC from transparent to opaque state is dependent on temperature and is triggered by the thermodynamic mechanism of reversible coil-globule transition, which results in a stable performance of the proposed device. Its solar modulation ability was studied using ultraviolet-visible- spectroscopy. Effect of MC concentration and various salts on the optical performance were investigated. It was found that the transition temperature the polymer can be tuned by varying MC concentration and by adding salts to the system. The tunability of transition temperature is a function of the concentration of salt and the type of anion in the salt. It was observed that the transition temperature of the window can be tuned between to , allowing a wide range of control over switching temperature. Controllable LCST, low freezing point, sustainable base material, scalable production, low cost, retrofit system makes them ideal candidates for smart window applications. </p>

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