Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 204-217).

Les réactions de transfert de charge entre molécules sont des processus fondamentaux dans de nombreux domaines scientifiques. En particulier, elles sont responsables de la conversion de la lumière en énergie chimique (photosynthèse) ou en énergie électrique dans les cellules solaires organiques (domaine du photovoltaïque). Ces dernières visent à produire de l’électricité à coût réduit afin de contribuer aux besoins en énergie renouvelable. Leur rendement reste toutefois faible (environ 5-6% contre 25% pour les cellules à base de silicium) et leur amélioration requiert l’optimisation de chaque étape du processus de transformation de l’énergie lumineuse en courant électrique : absorption de la lumière ; dissociation des excitations ; séparation des charges ; transport des charges. Les processus de dissociation d’excitations, de transport de charge, ainsi que de recombinaison de charges (diminuant le rendement de la cellule solaire) impliquent tous des réactions de transfert d’électron. Les transistors à effet de champ sont des composants fondamentaux en électronique, utilisés comme interrupteurs, déterminant si le courant passe ou non. Les transistors organiques se posent comme alternative moins couteuse aux transistors à base de silicium. Comme dans les cellules solaires, les processus de transfert de charge sont d’une importance primordiale, gouvernant ici la mobilité des charges au sein du dispositif. Rendre les dispositifs d’électroniques organiques concurrentiels par rapport aux dispositifs inorganiques nécessite de les rendre plus performants. Cette amélioration des performances passe, entre autres, par une optimisation des processus de transfert de charge. Dans ce contexte, cette thèse porte sur une étude théorique, basée sur des méthodes de chimie quantique et de mécanique moléculaire, de systèmes donneur-pont-accepteur, dans le but de mieux comprendre les processus de transfert de charge au sein de ces systèmes, en vue de leur utilisation en électronique organique. Ces systèmes présentent plusieurs avantages pour les cellules solaires : le fait de lier chimiquement le donneur et l’accepteur réduit la ségrégation de phase et la séparation des charges est facilitée lorsque les charges sont formées loin l’une de l’autre (grâce à la présence du pont) car l’attraction de Coulomb entre charges générées est réduite. Des molécules pontées peuvent également avoir d’autres applications, comme par exemple l’amélioration de la mobilité des charges dans un transistor organique à effet de champ en permettant un transport entre couches moléculaires. Nous nous sommes intéressés dans un premier temps à des structures modèles afin de mieux comprendre les mécanismes fondamentaux associés aux processus à transfert de charge. Nous avons ensuite appliqué cette méthode à trois types de systèmes réels, synthétisés et caractérisés expérimentalement. La première étude concerne le transport de charge au sein d’un copolymère conjugué donneur/accepteur, F8BT. La seconde concerne l’utilisation de systèmes pontés en vue d’une utilisation dans des transistors à effets de champs organiques. La dernière concerne l’injection de charges dans un matériau organique conjugué via une couche mono-moléculaire auto-assemblée. Pour terminer, nous nous sommes intéressés à l’influence de la dynamique structurale (vibrations moléculaires) sur les vitesses des réactions de transfert de charge dans des systèmes donneur-pont-accepteur.

The aim of this thesis is to achieve a deep understanding of the working mechanism of polymer based solar cells and to improve the device performance. Two types of the polymer based solar cells are studied here: all-polymer solar cells comprising macromolecular donors and acceptors based on poly(p-phenylene vinylene) and hybrid cells comprising a PPV copolymer in combination with a novel small molecule electron acceptor. To understand the interplay between morphology and photovoltaic properties in all-polymer devices, I compared the photocurrent characteristics and excited state properties of bilayer and blend devices with different nano-morphology, which was fine tuned by using solvents with different boiling points. The main conclusion from these complementary measurements was that the performance-limiting step is the field-dependent generation of free charge carriers, while bimolecular recombination and charge extraction do not compromise device performance. These findings imply that the proper design of the donor-acceptor heterojunction is of major importance towards the goal of high photovoltaic efficiencies. Regarding polymer-small molecular hybrid solar cells I combined the hole-transporting polymer M3EH-PPV with a novel Vinazene-based electron acceptor. This molecule can be either deposited from solution or by thermal evaporation, allowing for a large variety of layer architectures to be realized. I then demonstrated that the layer architecture has a large influence on the photovoltaic properties. Solar cells with very high fill factors of up to 57 % and an open circuit voltage of 1V could be achieved by realizing a sharp and well-defined donor-acceptor heterojunction. In the past, fill factors exceeding 50 % have only been observed for polymers in combination with soluble fullerene-derivatives or nanocrystalline inorganic semiconductors as the electron-accepting component. The finding that proper processing of polymer-vinazene devices leads to similar high values is a major step towards the design of efficient polymer-based solar cells. / Ziel dieser Dissertation ist es, die grundlegende Arbeitsweise von polymerbasierten Solarzellen zu verstehen und ihre Leistungsfähigkeit zu erhöhen. Zwei Arten von organischen Solarzellen werden untersucht: Solarzellen, bei denen sowohl Elektronendonator und akzeptor auf Poly(p-phenylen-vinylen) basieren sowie Zellen, bei denen ein PPV-Copolymer als Elektronendonator und organische kleine Moleküle als Elektronenakzeptor fungierten. Um die Zusammenhänge zwischen Morphologie und photovoltaischen Eigenschaften zu verstehen, untersuchte ich Photoströme sowie die Eigenschaften angeregter Zustände in Zweischicht- und Mischsolarzellen mit unterschiedlicher Nano-Morphologie, welche durch die Verwendung von Lösungsmitteln mit unterschiedlichen Siedetemperaturen modifiziert wurde. Die Hauptschlussfolgerung aus diesen Messungen ist, dass der effizienzlimitierende Faktor die feldabhängige Generation freier Ladungsträger ist, wohingegen bimolekulare Rekombination oder die Extraktion der Ladungsträger die Leistungsfähigkeit von Polymer-Polymer- Solarzellen nicht beeinträchtigen. Diese Ergebnisse legen nahe, dass die gezielte Einstellung der Donator-Akzeptor-Grenzfläche von besonderer Bedeutung zum Erreichen hoher Effizienzen ist. In Hybridsolarzellen aus Polymeren und kleinen Molekülen kombinierte ich das lochleitende konjugierte Polymer M3EH-PPV mit einem neuartigen Vinazen-Molekül als Elektronen-akzeptor. Dieses Molekül bietet die Möglichkeit, entweder aus einer Lösung heraus verarbeitet oder im Hochvakuum verdampft zu werden, wodurch eine Vielzahl an unterschiedlichen Probenstrukturen realisiert werden kann. Dadurch konnte ich zeigen, dass die Struktur der aktiven Schicht einen großen Einfluss auf die photovoltaischen Eigenschaften hat. Die Solarzellen erreichten einen Füllfaktor von bis zu 57% und eine Kurzschluss¬spannung von 1 V. In der Vergangenheit konnten bei polymerbasierten Solarzellen Füllfaktoren über 50% nur in Verbindung mit Fullerenen oder nanokristallinen anorganischen Halbleitern als Akzeptoren erreicht werden. Das Resultat, dass bei geeigneter Präparation der Polymer-Vinazen-Schicht vergleichbare Ergebnisse erzielt werden können, ist ein bedeutender Schritt hin zu effizienteren Polymersolarzellen.

Das Ziel dieser Arbeit ist die Untersuchung der aktiven Komponenten und ihrer Wechselwirkungen in teilorganischen Hybrid-Solarzellen. Diese bestehen aus einer dünnen Titandioxidschicht, kombiniert mit einer dünnen Polymerschicht. Die Effizienz der Hybrid-Solarzellen wird durch die Lichtabsorption im Polymer, die Dissoziation der gebildeten Exzitonen an der aktiven Grenzfläche zwischen TiO2 und Polymer, sowie durch Generation und Extraktion freier Ladungsträger bestimmt. Zur Optimierung der Solarzellen wurden grundlegende physikalische Wechselwirkungen zwischen den verwendeten Materialen sowie der Einfluss verschiedener Herstellungsparameter untersucht. Unter anderem wurden Fragen zum optimalen Materialeinsatz und Präparationsbedingungen beantwortet sowie grundlegende Einflüsse wie Schichtmorphologie und Polymerinfiltration näher betrachtet. Zunächst wurde aus unterschiedlich hergestelltem Titandioxid (Akzeptor-Schicht) eine Auswahl für den Einsatz in Hybrid-Solarzellen getroffen. Kriterium war hierbei die unterschiedliche Morphologie aufgrund der Oberflächenbeschaffenheit, der Film-Struktur, der Kristallinität und die daraus resultierenden Solarzelleneigenschaften. Für die anschließenden Untersuchungen wurden mesoporöse TiO2–Filme aus einer neuen Nanopartikel-Synthese, welche es erlaubt, kristalline Partikel schon während der Synthese herzustellen, als Elektronenakzeptor und konjugierte Polymere auf Poly(p-Phenylen-Vinylen) (PPV)- bzw. Thiophenbasis als Donatormaterial verwendet. Bei der thermischen Behandlung der TiO2-Schichten erfolgt eine temperaturabhängige Änderung der Morphologie, jedoch nicht der Kristallstruktur. Die Auswirkungen auf die Solarzelleneigenschaften wurden dokumentiert und diskutiert. Um die Vorteile der Nanopartikel-Synthese, die Bildung kristalliner TiO2-Partikel bei tiefen Temperaturen, nutzen zu können, wurden erste Versuche zur UV-Vernetzung durchgeführt. Neben der Beschaffenheit der Oxidschicht wurde auch der Einfluss der Polymermorphologie, bedingt durch Lösungsmittelvariation und Tempertemperatur, untersucht. Hierbei konnte gezeigt werden, dass u.a. die Viskosität der Polymerlösung die Infiltration in die TiO2-Schicht und dadurch die Effizienz der Solarzelle beeinflusst. Ein weiterer Ansatz zur Erhöhung der Effizienz ist die Entwicklung neuer lochleitender Polymere, welche möglichst über einen weiten spektralen Bereich Licht absorbieren und an die Bandlücke des TiO2 angepasst sind. Hierzu wurden einige neuartige Konzepte, z.B. die Kombination von Thiophen- und Phenyl-Einheiten näher untersucht. Auch wurde die Sensibilisierung der Titandioxidschicht in Anlehnung an die höheren Effizienzen der Farbstoffzellen in Betracht gezogen. Zusammenfassend konnten im Rahmen dieser Arbeit wichtige Einflussparameter auf die Funktion hybrider Solarzellen identifiziert und z.T. näher diskutiert werden. Für einige limitierende Faktoren wurden Konzepte zur Verbesserung bzw. Vermeidung vorgestellt. / The main objective of this thesis is to study the active components and their interactions in so called organic hybrid solar cells. These consist of a thin inorganic titanium dioxide layer, combined with a polymer layer. In general, the efficiency of these hybrid solar cells is determined by the light absorption in the donor polymer, the dissociation of excitons at the heterojunction between TiO2 and polymer, as well as the generation and extraction of free charge carriers. To optimize the solar cells, the physical interactions between the materials are modified and the influences of various preparation parameters are systematically investigated. Among others, important findings regarding the optimal use of materials and preparation conditions as well as detailed investigations of fundamental factors such as film morphology and polymer infiltration are presented in more detail. First, a variety of titanium dioxide layer were produced, from which a selection for use in hybrid solar cells was made. The obtained films show differences in surface structure, film morphology and crystallinity, depending on the way how the TiO2 layer has been prepared. All these properties of the TiO2 films may strongly affect the performance of the hybrid solar cells, by influencing e.g. the exciton diffusion length, the efficiency of exciton dissociation at the hybrid interface, and the carrier transport properties. Detailed investigations were made for mesoporous TiO2 layer following a new nanoparticle synthesis route, which allows to produce crystalline particles during the synthesis. As donor component, conjugated polymers, either derivatives of cyclohexylamino-poly(p-phenylene vinylene) (PPV) or a thiophene are used. The preparation routine also includes a thermal treatment of the TiO2 layers, revealing a temperature-dependent change in morphology, but not of the crystal structure. The effects on the solar cell properties have been documented and discussed. To take advantage of the nanoparticle synthesis, the formation of crystalline TiO2 particles by UV crosslinking and first solar cell measurements are presented. In addition to the nature of the TiO2 layer, the influence of polymer morphology is investigated. Different morphologies are realized by solvent variation and thermal annealing. It is shown that, among other factors, the viscosity of the polymer solution and the infiltration into the TiO2 layer mainly affects the efficiency of the solar cell. Another approach to increase the efficiency is the development of new hole-conducting polymers that absorb over a wide spectral range and which are adjusted to the energy levels of TiO2. Also new concepts, for example, the combination of thiophene- and phenyl-units into a copolymer are investigated in more detail. In summary, important parameters influencing the properties of hybrid solar cells are identified and discussed in more detail. For some limiting factors concepts to overcome these limitations are presented.

The use of solar cells for energy production has indeed a bright future. Reduction of cost for fabrication along with increased efficiency are key features for a market boom, both achieved as a result of increased knowledge of the technology. Especially the thin film solar cell technology with absorbers made of Cu(In,Ga)Se2 (CIGS) is promising since it has proven high power conversion efficiency in combination with a true potential for low cost fabrication. In this thesis different recipes for fabrication of the Cu(In,Ga)Se2 absorber layer have been studied. The deposition technique used has been co-evaporation from elemental sources. For all depositions the substrate has been heated to a constant temperature of 500 ºC in order for the growing absorber to form a chalcopyrite phase, necessary for the photovoltaic functionality. The selenium has been evaporated such to always be in excess during depositions whereas the metal ratio Cu/(In+Ga) has been varied according to different recipes but always to be less than one at the end of the process. In the work emphasis has been on the radiative properties of the CIGS film during growth. The substrate heater has been temperature controlled to maintain the constant set temperature of the substrate, regardless of varying emitted power caused by changing surface emissivity. Depending on the growth conditions the emissivity of the growing film is changing, leading to a readable variation in the electrical power to the substrate heater. Since the thermal radiation from the substrate during growth has been of central focus, this has been studied in detail. For this reason the substrate has been treated as an optical stack composed of glass/Mo/Cu(In,Ga)Se2/CuxSe which determine the thermally radiated power by its emissivity. An optical model has been adopted to simulate the emissivity of the stack. In order to use the model, the optical constants for Cu(In,Ga)Se2 and CuxSe have been derived for the wavelength interval 2 μm to 20 μm. The simulation of the emissivity of the stack during CIGS growth agreed well with what has been seen for actual growth. Features of the OP-signal could hereby be explained as a result of film thickness of Cu(In,Ga)Se2 and CuxSe respectively. This is an important knowledge for an efficient fabrication in large scale.

In this thesis we synthesize two organic materials, one is discotic liquid crystal Acid-6, and the other is novel discotic liquid crystal polymer DLC-PAM. After demonstrating the molecular structures of Acid-6 and DLC-PAM by FT-MS, 1H-NMR and FT-IR, we use the two materials as photo-sensitized dyes for dye-sensitized solar cells(DSSCs) and manufacture two kinds of cells. We use polyacrylamide(PAM) as main chain of the novel discotic liquid crystal polymer DLC-PAM and graft the discotic liquid crystal monomer Acid-6 onto PAM by chemical synthesis. DLC-PAM belongs to side-chain liquid crystal polymer, and it can show the properties of it¡¦s discotic liquid crystal function. One of the properties is absorption of visible light. By observing the UV-Vis spectrum, we can realize the absorption band is located between 200 ~ 450 nm and confirm that it is able to be a photo-sensitized dye. Another property of discotic liquid crystal is the self-assembly ability, the moleculars can assemble into hexagonal columnar structure by themselves, and the property enable discotic liquid crystal to have better mobility. In this part, we can demonstrate DLC-PAM and Acid-6 really have hexagonal columnar structure by X-ray diffractmeter. After qualitative demonstrating and optical analysis, we use DLC-PAM and Acid-6 as photo-sensitized dyes for DSSCs and manufacture two kinds of cells successfully. The more photocurrent occur when the two DSSCs are woking. Besides, the two DSSCs have good performance on power conversion efficiency which can achieve 0.047 % for DLC-PAM and 0.364 % for Acid-6. Therefore, in this research we prove that DLC-PAM and Acid-6 are able to be photo-sensitized dyes for DSSCs and successfully demonstrate that using the two materials to manufacture DSSCs is feasible.

Cu(In,Ga)Se2 (CIGS) is one of the most promising semiconductor compounds for large-scale production of efficient, low-cost thin film solar cells, and several research institutes have announced their plans for CIGS production lines. But for the CIGS technology to become a commercial success, a number of issues concerning manufacturability, product definition, and long-term stability require further attention. Several studies indicate that CIGS-based modules are stable over many years in field operation. At the same time, it is shown in the present work that they may have difficulties in passing standard accelerated lifetime test procedures like the IEC 1646 damp heat test. In particular, CIGS modules are sensitive to humidity penetrating through the module encapsulation, which will increase the resistive losses in the front contact and cause severe corrosion of the back contact. It is also shown that cells experience degradation in both voltage and fill factor, and the causes of these effects are addressed. By concentrating the light falling onto a solar cell, the device will deliver a higher power output per illuminated absorber area, which can lower the electricity production costs. For CIGS-based solar cells, low-concentrated illumination could be an economically viable approach. In this work it is shown that the yearly performance of a photovoltaic system with CIGS modules can be significantly improved at a moderate cost by using parabolic aluminum mirrors as concentrating elements. However, in order to avoid detrimental power losses due to high temperatures and current densities, the modules need to be designed for the higher light intensity and to be sufficiently cooled during operation. A design where the front contact of the module is assisted by a metal grid has shown promising results, not only for concentrated illumination but also for normal operation. The benefits are enhanced window processing tolerance and throughput, as well as improved degrees of freedom of the module geometry.

This rapport contains an examination of the energy consumption of a kindergarten, which areas that have the largest impact on the energy consumption and what can be done to reduce those areas in ways that are relatively easy and profitable. It is also analyzed if it is possible to reduce the energy consumption from today’s consumption to a consumption that fulfils the demands placed on low energy houses by FEBY. The focus has been on reducing the energy consumption of the areas ventilation, heating system and hot water system, since those seemed to be the easiest ones to affect and since the building is quite recently built. There are different kinds of ventilation systems, at the moment the building have a CAV-system, which means that the ventilation is too high during large parts of the day. There are different ways to manage the ventilation system, for example presence detection, humidity sensors, CO2 sensors, temperature sensors and season adjustment. Many of those are in the end dependent on CO2 sensors to guarantee a good indoor climate, therefore the focus have been placed on this system.   The building is heated through district heating which is relatively easy to connect to a couple of sun panels to contribute to the heating system and hot water system. There are different ways of connecting district heating with solar panels and those are described, as well as the cost and the repayment time. A comparison with a building with an electric heating system has been made as well. It is important to get solutions that are profitable, that the repayment time isn’t too long. Solar cells and wind turbines are examined as well, but the repayment time for solar cells are too long at the moment. The repayment time for solar cells varies between 42 - 75 years, while the expected lifetime is 25 years. Concerning ventilation, a reduced ventilation of 10, 20, 30, 40 and 50 % have been examined. With only reduced ventilation the demands on low energy houses could not be matched, but it was possible in two cases with the use of solar panels. The usage of a wind turbine meant that the ventilation had to be reduced even less to match the demands on low energy houses. The repayment times for the solar panels and the wind turbine are both around 14 years. / Rapporten behandlar en undersökning av energiförbrukningen vid en projekterad förskola och vilka poster som har störst inverkan på energiförbrukningen, samt vad som kan göras för att åtgärda dessa på ett sätt som är relativt enkelt och som är lönsamt. Det ses över om det är möjligt att få ner energiförbrukningen från dagens förbrukning som uppfyller BBR:s krav, till att uppfylla de lägre energikraven som gäller för minienergihus enligt FEBY. Med utgångspunkt i energiförbrukningsberäkningen som gjorts och det faktum att förskolan är relativt nybyggd så har fokus lagts på att minska ner posterna ventilation, värmesystemet och varmvattnet då dessa är de poster som är lättast att påverka. När det gäller ventilation finns olika styrsätt, byggnaden har i nuläget ett CAV-system, vilket innebär att ventilation under stora delen av dagen är för hög. Det finns olika saker att styra ventilationen och minska ner den på, däribland närvarogivare, fuktgivare, koldioxidgivare, temperaturgivare samt årstidsanpassning. Många av dessa är dock i slutändan beroende av koldioxidgivare för att garantera inomhusklimatet, så därför har fokus lagts på detta system. Byggnaden värms upp via fjärrvärme och det är relativt enkelt att koppla på solfångare för hjälp av uppvärmning av värmesystemet och varmvattnet. Det finns olika sätt att koppla in solfångare på system med fjärrvärme och de olika sätten beskrivs och undersöks, liksom kostnad och återbetalningstid för en anläggning med solfångare. En jämförelse med en byggnad med eluppvärmning har också gjorts. Det är viktigt att få ekonomisk lönsamhet i det hela och således att återbetalningstiden inte ska vara för lång. Även solceller och vindkraftverk tas upp, dock är återbetalningstiden för solceller i nuläget alltför lång för att vara ekonomiskt försvarbart. Återbetalningstiden för solceller varierar mellan 42 – 75 år, medan den beräknade livslängden ligger på 25 år. När det gäller ventilationen så har minskad ventilation med 10, 20, 30, 40 och 50 % undersökts. Med enbart minskad ventilation kan inte kravet för lågenergihus uppfyllas, men inräknat solfångare så nåddes i två fall lågenergihus. Till sist så innebar medräknandet av ett vindkraftverk att ventilationen inte behövdes minskas lika mycket för att uppfylla kraven för lågenergihus. Återbetalningstiden för solfångarna beräknades till 14 år och återbetalningstiden för vindkraftverket till 14 år.

The photophysical properties of a series of Zn (II) porphyrins adsorbed onto a semiconductor were investigated using steady-state absorbance and emission measurements. The ability of the porphyrins to undergo triplet-triplet annihilation (TTA), a photophysical process through which photons in the red and near-infrared (NIR) regions of the optical spectrum can be converted into higher energy photons (upconversion), was explored. Aggregation capabilities were determined to verify possibility of these molecules to undergo triplet-triplet annihilation (TTA). TTA has significant potential for increasing the efficiency of dye-sensitized solar cells (DSSCs) by upconverting photons in the energy rich NIR region of the solar spectrum. A key requirement for efficient TTA is aggregation of the sensitizer dye, and in this thesis, we have examined the aggregation of porphyrins in TiO2-based sol-gel films. Solution phase absorption and emission studies were conducted using zinc (II) tetraphenylporphyrin and three of its functionalized derivatives, tetra(4-aminophenyl)porphyrin Zn(II), tetra(4-carboxyphenyl)porphyrin Zn(II), and tetra(4-sulfonatophenyl)porphyrin Zn(II), to evaluate their potential as DSSC sensitizers on TiO2 thin films. Mesoporous TiO2 thin films were synthesized, using a polymer-templating sol-gel route, and characterized with tunneling electron microscopy (TEM), atomic force microscopy (AFM), and UV-Vis absorbance measurements. Spectroscopy measurements were also carried out on porphyrin-sensitized TiO2 thin films and compared to solution-based results. A simple DSSC was constructed and used to further explore the application of zinc (II) porphyrin sensitizers in photovoltaic applications.

El processament convencional de materials d'òxid de titani (TiO2) inherentment implica un consum energètic important i ha esdevingut una limitació tecnològica per a la fabricació de dispositius emprant substrats termolàbils així com per a la preparació de materials híbrids orgànic/TiO2. Aquesta tesi doctoral tracta del desenvolupament de processos químics per a la preparació de capes i pols de TiO2 d'acord amb principis de Química Verda, posant especial èmfasi en el processament a baixa temperatura. Plantejaments simples, benignes amb el medi ambient i de baix cost són els desitjats sota aquestes directrius. A més a més, els mètodes a baixa temperatura (idealment fins a un màxim proper a 100ºC) haurien de donar lloc a materials que exhibeixin propietats similars a aquells processats a alta temperatura o tractats solvotermalment. S'ha focalitzat especial interès en la recerca d'aplicacions pràctiques dels materials produïts en camps com la conversió d'energia solar i materials actuadors. / El procesamiento convencional de materiales de óxido de titanio (TiO2) inherentemente implica un consumo energético importante y ha resultado una limitación tecnológica para la fabricación de dispositivos utilizando substratos termolábiles así como para la preparación de materiales híbridos orgánico/TiO2. Esta tesis doctoral trata el desarrollo de procesos químicos suaves para la preparación de capas y polvos de TiO2 de acuerdo con principios de Química Verde, poniendo especial énfasis en el procesamiento a baja temperatura. Planteamientos simples, benignos con el medioambiente y de bajo conste son los deseados bajo estas directrices. Además, los métodos a baja temperatura (idealmente hasta un máximo próximo a 100ºC) deberían dar lugar a materiales que exhiban propiedades similares a aquellos procesados a alta temperatura o tratados solvotermalmente. Se ha centrado especial interés en la búsqueda de aplicaciones prácticas de los materiales producidos en campos como la conversión de energía solar y materiales actuadores. / Conventional high-temperature processing of titanium dioxide (TiO2) materials inherently implies important energy consumption and has became a technological limitation for fabricating devices employing thermolabile substrates as well as preparing hybrid organic/TiO2 materials. This PhD thesis deals with the development of chemical processes for preparing TiO2 films and powders fitting Green Chemistry principles, putting special emphasis on low-temperature processing. Simple, environmentally benign and low-cost approaches are desired upon these guidelines. Moreover, low-temperature methods (ideally up to a maximum closer to 100ºC) should give rise to materials exhibiting properties similar than those processed at high temperature or solvothermally treated. Special interest has been focused on finding practical applications of the as-prepared materials in fields such as solar energy conversion and actuating materials.