Research on pi-conjugated organic materials in the recent past has produced enormous developments in the field of organic electronics and it is mainly due to their applications in electronic devices such as organic field effect transistors (OFETs), organic light emitting diodes (OLEDs) and organic photovoltaic cells (OPVs). The primary goal of this research work is to design and synthesize high performing charge transport organic semiconductors. One of the criteria for better performance of the organic thin film transistor (OTFT) is to have high uniform thin film morphology of the organic semiconductor layer on the substrate. The first project in this dissertation has been directed towards improving the thin film morphology of the functionalized pentacenes through liquid crystalline behaviour. The results have suggested the possibility of thermotropic liquid crystalline phases in 6,13-bis(diisopropylhexylsilylethynyl) pentacene which has no pi-stacking in its solid state and the presence of silyl group at the peri-position is crucial for the stability of the functionalized pentacenes. In the second project, i have investigated the effect of alkyl groups with varying chain length on the anthradithiophene chromophore on the performance of the charge transporting devices. Organic blend cell based on solution processable 2,8-diethyl-5,12-bis(triethylsilylethynyl) anthradithiophene has showed 1% power conversion efficiency and the performance is mainly attributed to the large crystalline phase segregation of the functionalized anthradithiophene from the amorphous soluble fullerene derivative matrix. OTFT study on alkyl substituted functionalized anthradithiophenes suggested the need of delegate balance between thin film morphology and the crystal packing. Third project has been directed towards synthesizing halogen substituted functionalized anthradithiophenes and their influence in the performance of OFETs. OTFT made of 2,8-difluoro-5,12-bis(triethylsilylethynyl) anthradithiophene produced devices with thin film hole mobilities greater than 1 cm2/Vs. The result suggested that the device is not contact limited rather this high performance OTFTs are due to the contact induced crystallinity of the organic semiconductor.

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The goal of this paper is to find out how solar cells can improve energy efficiency on-board M/S Sydfart. The paper is based on a number of energy measurements on board the M/S Sydfart. The solar surface is calculated by measuring the available space for installing solar panels. Global radiation data is taken from STRÅNG's database, the data is then used to calculate the theoretical power produced by the solar cells. Energy efficiency is analysed in two ways. The first analysis focuses on how much of the daily energy usage that can be covered with solar cells. The second analysis focuses on the change of EEOI attainable with solar cells installed. The electrical energy consumption on-board M/S Sydfart, during the summer, is almost entirely covered with solar cells. The paper however shows some disadvantages. During the winter, the produced electrical energy from solar cells are low and an unreasonably large area of solar panels is required to cover the electricity demand. Two scenarios are evaluated. In scenario one, all the space available for the installation of photovoltaic panels is used. This gives a large energy surplus during summer. In scenario two, only half of the surface is used to install solar panel. This results in a smaller energy surplus without any significant loss of usable energy. Given that M/S Sydfart has limited ability to take advantage of energy surplus, the second scenario is recommended. The result shows that energy efficiency will be improved. Depending on the season, EEOI can be improved between 0.5 % and 12%. There is no demand for improvement in EEOI from IMO. It is up to the shipping companies themselves to set internal targets for improvement. / Målet med denna uppsats är att ta reda på hur solceller kan förbättra energieffektiviteten ombord M/S Sydfart. Uppsatsen baseras på ett antal energimätningar ombord M/S Sydfart. Solcellernas yta beräknas med hänsyn taget till tillgänglig yta för att installera solpaneler. Globalstrålningsdata kommer ifrån STRÅNG`s databas, den datan används sedan för att beräkna en teoretisk producerad effekt utav solcellerna. Energieffektiviteten analyseras på två sätt. Den första analysen ser på hur mycket av den dagliga energiförbrukningen som kan tillgodogöras med solceller. Den andra analysen baseras på hur stor för- ändring av EEOI som kan uppnås med installerade solceller. Elenergibehovet ombord M/S Sydfart, under sommarhalvåret, kan nästan helt täckas med solceller. Uppsatsen visar dock en del nackdelar med solceller. Under vinterhalvåret är den producerade elenergin från solcellerna låg och en orimligt stor yta solcellsmoduler behövs för att täcka elenergibehovet. Två scenarion utvärderas. I scenario ett utnyttjas all tillgänglig yta för installation av solcellsmoduler. Detta ger ett stort energiöverskott på sommarhalvåret. I scenario två halveras ytan för solcellsmoduler och energiöverskottet blir då mindre. Med hänsyn till att M/S Sydfart har begränsad möjlighet att ta till vara på energiöverskottet, rekommenderas scenario två. Resultatet visar att energieffektiviteten kommer att förbättras. Beroende på årstid, kan EEOI förbättras mellan 0.5% och 12 %. Något krav på förbättring av EEOI finns inte från IMO. Det är rederierna själva som sätter upp interna mål för förbättring.

The goal of this dissertation work was to develop pulsed terahertz radiation techniques and use them to study different properties of the semiconductor materials and semiconductor devices. Three groups of materials were investigated: GaAsBi, GaAs nanowires, copper-indium chalcogenide. The used techniques are THz-TDS, optical pump – THZ probe, optical pump – optical probe and THz excitation spectral measurements. The main results that were presented in this dissertation are the following: thermal annealing has resulted in the shortening of electron lifetime in GaAsBi to picosecond values, which is important achievement for the application of this material in THz range components. In GaAsBi layers with larger than 10% Bi content absorption bleaching recovering on the picosecond time scale and its saturation can be realized when the wavelengths of the optical signals are as long as 1600 nm. The results of these studies can be applied in the production of SESAM with bismide absorption layer. The samples with GaAs nanowires emit THz radiation several times better than the bulk GaAs substrates due to enhanced light absorption because of localized surface plasmon resonances in GaAs nanowires. THz emission efficiency from thin copper-indium chalcogenide layers strongly depends on their stoichiometry and on the parameters of the top transparent contact layers, thus it can be used for the mapping of built-in electric fields in solar cells made from these layers. / Šio darbo tikslas buvo susipažinti su terahercinių impulsų generavimo ir detektavimo būdais, įsisavinti įvairias terahercinių impulsų panaudojimo metodikas bei pritaikyti jas puslaidininkių medžiagų ir puslaidininkinių prietaisų tyrimui. Buvo tirtos trys medžiagų grupės: GaAsBi, GaAs nanovielutės ir Cu – In chalkogenidai. Tyrimui buvo naudojamos: THz – TDS, optinio žadinimo – THz zondavimo, optinio žadinimo – optinio zondavimo bei THz sužadinimo spektroskopijos metodikos. Pagrindiniai rezultatai aprašyti disertacijoje yra šie: GaAsBi bandinių atkaitinimas stipriai sumažino krūvininkų gyvavimo trukmes, kas yra naudinga THz komponentų gamyboj. Optinio praskaidrėjimo efektas ir pikosekundžių eilės krūvininkų gyvavimo trukmės GaAsBi epitaksiniuose sluoksniuose su 10% ir daugiau Bi atomų stebimas žadinant juos optine spinduliuote, kurios bangos ilgiai siekia iki 1600 nm. Šios GaAsBi bandinių savybės leidžia juos priakyti įsisotinančių sugėriklių veidrodžių gamyboje. Bandiniai su GaAs nanovielutėmis emituoja THz spinduliuotę kelis kartus geriau nei GaAs padėklas, dėl padidėjusios sugerties, kurią skatina paviršinių optinių plazmonų rezonansai GaAs nanovielutėse. THz emisijos efektyvumas iš Cu-In chalkogenidų sluoksnių stipriai priklauso nuo jų stechiometrijos ir viršutinio skaidraus kontakto parametrų, ir gali būti naudojamas saulės elementų, pagamintų šių sluoksnių pagrindu, vidinių elektrinių laukų tyrimui.

Šio darbo tikslas buvo susipažinti su terahercinių impulsų generavimo ir detektavimo būdais, įsisavinti įvairias terahercinių impulsų panaudojimo metodikas bei pritaikyti jas puslaidininkių medžiagų ir puslaidininkinių prietaisų tyrimui. Buvo tirtos trys medžiagų grupės: GaAsBi, GaAs nanovielutės ir Cu – In chalkogenidai. Tyrimui buvo naudojamos: THz – TDS, optinio žadinimo – THz zondavimo, optinio žadinimo – optinio zondavimo bei THz sužadinimo spektroskopijos metodikos. Pagrindiniai rezultatai aprašyti disertacijoje yra šie: GaAsBi bandinių atkaitinimas stipriai sumažino krūvininkų gyvavimo trukmes, kas yra naudinga THz komponentų gamyboj. Optinio praskaidrėjimo efektas ir pikosekundžių eilės krūvininkų gyvavimo trukmės GaAsBi epitaksiniuose sluoksniuose su 10% ir daugiau Bi atomų stebimas žadinant juos optine spinduliuote, kurios bangos ilgiai siekia iki 1600 nm. Šios GaAsBi bandinių savybės leidžia juos priakyti įsisotinančių sugėriklių veidrodžių gamyboje. Bandiniai su GaAs nanovielutėmis emituoja THz spinduliuotę kelis kartus geriau nei GaAs padėklas, dėl padidėjusios sugerties, kurią skatina paviršinių optinių plazmonų rezonansai GaAs nanovielutėse. THz emisijos efektyvumas iš Cu-In chalkogenidų sluoksnių stipriai priklauso nuo jų stechiometrijos ir viršutinio skaidraus kontakto parametrų, ir gali būti naudojamas saulės elementų, pagamintų šių sluoksnių pagrindu, vidinių elektrinių laukų tyrimui. / The goal of this dissertation work was to develop pulsed terahertz radiation techniques and use them to study different properties of the semiconductor materials and semiconductor devices. Three groups of materials were investigated: GaAsBi, GaAs nanowires, copper-indium chalcogenide. The used techniques are THz-TDS, optical pump – THZ probe, optical pump – optical probe and THz excitation spectral measurements. The main results that were presented in this dissertation are the following: thermal annealing has resulted in the shortening of electron lifetime in GaAsBi to picosecond values, which is important achievement for the application of this material in THz range components. In GaAsBi layers with larger than 10% Bi content absorption bleaching recovering on the picosecond time scale and its saturation can be realized when the wavelengths of the optical signals are as long as 1600 nm. The results of these studies can be applied in the production of SESAM with bismide absorption layer. The samples with GaAs nanowires emit THz radiation several times better than the bulk GaAs substrates due to enhanced light absorption because of localized surface plasmon resonances in GaAs nanowires. THz emission efficiency from thin copper-indium chalcogenide layers strongly depends on their stoichiometry and on the parameters of the top transparent contact layers, thus it can be used for the mapping of built-in electric fields in solar cells made from these layers.

Abstract Methylammonium lead (II) iodide has recently attracted considerable interest which may lead to substantial developments of efficient and inexpensive industrial photovoltaics. The application of this material as a light-absorbing layer in solid-state solar cells leads to impressive efficiency of over 22% in laboratory devices. However, for industrial applications, fundamental issues regarding their thermal and moisture stability need to be addressed. MAPbI3 belongs to the perovskite family of materials with the general formula ABX3 ,where is the organic cation (methylammonium) which is reported to be a major source of instability. In this work, a variety of alkyammonium lead (II) iodide materials have been synthesized by changing the organic cation, to study the relationship between the structural and physical properties of these materials. [(A)PbI3] and (A)PbI4 series were studied. Three dimensional (3D) networks (MAPbI3,MAPbBr3), two dimensional (2D) layered systems (BdAPbI4, HdAPbI4, OdAPbI4), and one dimensional (1D) columns (EAPbI3, PAPbI3, EAPb2I6) were found for the materials. [PbI6] octahedral structural units were repeated through the material network depending on the dimensionality and connectivity of the materials. Where a bulkier cation was introduced, the crystallographic unit cell increased in size which resulted in lower symmetry crystals. The connectivity of the unit cells along the material networks was found to be based on corner-sharing and face-sharing. Lower dimensionality resulted in larger bandgaps and lower photoconductivity, and hence a lower light conversion efficiency for the related solar cells. The thermal and moisture stability was greater in the 1D and 2D materials with bulkier organic cations than with methylammonium. In total, an overview is provided of the relationship between the chemical dimensionality and physical properties of the organic-inorganic lead halide materials with focus on the solar cell application. / Svenska sammandrag: Metylammoniumbly(II)jodid har under de senaste åren genererat ett stort intresse som ett möjligt material for utveckling av effektiva och på industriell skala billiga solceller. Detta material har använts som ljusabsorberande skikt i fasta solceller med imponerande omvandlingseffektiviteter på över 22% för solceller i laboratorieskala. För att denna nya typ av solceller ska bli intressanta för produktion på industriell skala, så behöver grundläggande frågeställningar kring materialens stabilitet avseende högre temperaturer och fukt klargöras. MAPbI3 har formellt perovskitstruktur med den allmänna formel ABX3, där A utgörs av den organiska katjonen (metyammoniumjonen) och som kan kopplas till materialets instabilitet. I denna avhandling har olika alkylammoniumbly(II)jodidmaterial syntetiserats där den organiska katjonen modifierats med syftet att studera växelverkan mellan struktur och fysikaliska egenskaper hos de resulterande materialen. Material av olika dimensionalitet erhölls; tredimensionella (3D) nätverk (MAPbI3, MAPbBr3), tvådimensionella (2D) skiktade strukturer (BdAPbI4, HdAPbI4, OdAPbI4), och endimensionella (1D) kedjestrukturer (EAPbI3, PAPbI3, EAPb2I6). Flera nya lågdimensionella material (2D och 1D) tillverkats och karaktäriserats för första gången. Enkristalldiffraktometri har använts för att erhålla materialens atomära struktur. Strukturen hos material tillverkade i större mängder konfirmerades genom jämförelse mellan resultat från pulverdiffraktion och enkristalldiffraktion. Den oktaedriska strukturenheten [PbI6] utgör ett återkommande tema i materialen sammankopplade till olika dimensioner. Då större organiska katjoner används karaktäriseras i regel strukturerna av större enhetsceller och lägre symmetri. De lågdimensionella materialen ger typiskt störe elektroniskt bandgap, lägre fotoinducerad ledningsförmåga och därför sämre omvandlingseffektiviteter då de används i solceller. De lågdimensionella materialen (1D och 2D) som baseras på de större organiska katjonerna uppvisar bättre stabilitet med avseende på högre tempereratur och fukt. De tvådimensionella materialens elektroniska struktur har karaktäriserats med hjälp av röntegenfotoelektronspektroskopi, liksom röntgenabsorptions- och emissionsspektroskopi. Resultat från teoretiska beräkningar stämmer väl överens med de experimentella resultaten, och de visar att materialens valensband huvudsakligen består av bidrag från atomorbitaler hos jod, medan atomorbitaler från bly främst bidrar till edningsbandet. Sammantaget erbjuder avhandlingen en översikt av sambandet mellan kemisk dimensionalitet och fysikaliska egenskaper hos ett antal organiska/oorganiska blyhalogenidmaterial med fokus på tillämpning i solceller. / <p>QC 20170123</p>

We report the synthesis of ultra-high aspect ratio copper nanowires (CuNW) and fabrication of CuNW-based transparent conductive electrodes (TCE) with high optical transmittance (> 80%) and excellent sheet resistance (R-s < 30 Omega/sq). These CuNW TCEs are subsequently hybridized with aluminum-doped zinc oxide (AZO) thin-film coatings, or platinum thinfilm coatings, or nickel thin-film coatings. Our hybrid transparent electrodes can replace indium tin oxide (ITO) films in dye-sensitized solar cells (DSSCs) as either anodes or cathodes. We highlight the challenges of integrating bare CuNWs into DSSCs, and demonstrate that hybridization renders the solar cell integrations feasible. The CuNW/AZO-based DSSCs have reasonably good open-circuit voltage (V-oc = 720 mV) and short-circuit current-density (J(sc) = 0.96 mA/cm(2)), which are comparable to what is obtained with an ITO-based DSSC fabricated with a similar process. Our CuNW-Ni based DSSCs exhibit a good open-circuit voltage (V-oc = 782 mV) and a decent short-circuit current (J(sc) = 3.96 mA/cm2), with roughly 1.5% optical-to-electrical conversion efficiency.

In 2012 the net world electricity generation was 21.56 trillion kilowatt hours. Photovoltaics only accounted for only 0.1 trillion kilowatt hours, less than 1 % of the total power. Recently there has been a push to convert more energy production to renewable sources. In recent years a great deal of interest has been shown for dye sensitized solar cells. These devices use inexpensive materials and have reported efficiencies approaching 12% in the lab. Here methods have been studied to improve upon these, and other, devices. Different approaches for the addition of gold nanoparticles to TiO2 films were studied. These additions acted as plasmonic and light scattering enhancements to reported dye sensitized devices. These nanoparticle enhancements generated a 10% efficiency in device performance for dye sensitized devices. Quantum dot (QD) sensitized solar cells were prepared by successive ionic layer adsorption and reaction (SILAR) synthesis of QDs in mesoporous films as well as the chemical attachment of colloidal quantum dots using 3-mercaptopropionic acid (3-MPA). Methods of synthesizing a copper sulfide (Cu2S) counter electrode were investigated to improve the device performance. By using a mesoporous film of indium tin oxide nanoparticles as a substrate for SILAR growth of Cu2S catalyst, an increase in device performance was seen over that of devices using platinum. These devices did suffer from construction drawbacks. This lead to the development of 3D nanostructures for use in Schottky photovoltaics. These high surface area devices were designed to overcome the recombination problems of thin film Schottky devices. The need to deposit a transparent top electrode limited the success of these devices, but did lead to the development of highly ordered metal nanotube arrays. To further explore these nanostructures depleted heterojunction devices were produced. Along with these devices a new approach to depositing lead sulfide quantum dots was developed. This electrophoretic deposition technique uses an applied electric field to deposit nanoparticles onto a substrate. This creates the possibility for a low waste method for depositing nanocrystals onto nanostructured substrates.

The long-term outdoor durability of dye-sensitized solar cells (DSSCs) is still a challenging issue for the large-scale commercial application of this promising photovoltaic technique. In order to study the degradation mechanism of DSSCs, ageing tests under selected accelerating conditions were carried out. The electrolyte is a crucial component of the device. The interactions between the electrolyte and other device components were unraveled during the ageing test, and this is the focus of this thesis. The dynamics and the underlying effects of these interactions on the DSSC performance were studied. Co(bpy)32+/3+-mediated solar cells sensitized by triphenylamine-based organic dyes are systems of main interest. The changes with respect to the configuration of both labile Co(bpy)32+ and apparently inert Co(bpy)33+ redox complexes under different ageing conditions have been characterized, emphasizing the ligand exchange problem due to the addition of Lewis-base-type electrolyte additives and the unavoidable presence of oxygen. Both beneficial and adverse effects on the DSSC performance have been separately discussed in the short-term and long-term ageing tests. The stability of dye molecules adsorbed on the TiO2 surface and dissolved in the electrolyte has been studied by monitoring the spectral change of the dye, revealing the crucial effect of cation-based additives and the cation-dependent stability of the device photovoltage. The dye/TiO2 interfacial electron transfer kinetics were compared for the bithiophene-linked dyes before and after ageing in the presence of Lewis base additives; the observed change being related to the light-promoted and Lewis-base-assisted performance enhancement. The effect of electrolyte co-additives on passivating the counter electrode was also observed. The final chapter shows the effect of electrolyte composition on the electrolyte diffusion limitation from the perspectives of cation additive options, cation concentration and solvent additives respectively. Based on a comprehensive analysis, suggestions have been made regarding lithium-ion-free and polymer-in-salt strategies, and also regarding cobalt complex degradation and the crucial role of Lewis base additives. The fundamental studies contribute to the understanding of DSSC chemistry and provide a guideline towards achieving efficient and stable DSSCs. / <p>QC 20160517</p>