abstract: The origins of carrier mobility (μe) were thoroughly investigated in hydrogenated indium oxide (IO:H) and zinc-tin oxide (ZTO) transparent conducting oxide (TCO) thin films. A carrier transport model was developed for IO:H which studied the effects of ionized impurity scattering, polar optical phonon scattering, and grain boundary scattering. Ionized impurity scattering dominated at temperatures below ~240 K. A reduction in scattering charge Z from +2 to +1 as atomic %H increased from ~3 atomic %H to ~5 atomic %H allowed μe to attain >100 cm^2/Vs at ~5 atomic %H. In highly hydrogenated IO:H, ne significantly decreased as temperature increased from 5 K to 140 K. To probe this unusual behavior, samples were illuminated, then ne, surface work function (WF), and spatially resolved microscopic current mapping were measured and tracked. Large increases in ne and corresponding decreases in WF were observed---these both exhibited slow reversions toward pre-illumination values over 6-12 days. A hydrogen-related defect was proposed as source of the photoexcitation, while a lattice defect diffusion mechanism causes the extended decay. Both arise from an under-coordination of the In. An enhancement of μe was observed with increasing amorphous fraction in IO:H. An increase in population of corner- and edge-sharing polyhedra consisting of metal cations and oxygen anions is thought to be the origin. This indicates some measure of medium-range order in the amorphous structure, and gives rise to a general principle dictating μe in TCOs---even amorphous TCOs. Testing this principle resulted in observing an enhancement of μe up to 35 cm^2/Vs in amorphous ZTO (a-ZTO), one of the highest reported a-ZTO μe values (at ne > 10^19 cm^-3) to date. These results highlight the role of local distortions and cation coordination in determining the microscopic origins of carrier generation and transport. In addition, the strong likelihood of under-coordination of one cation species leading to high carrier concentrations is proposed. This diverges from the historical indictment of oxygen vacancies controlling carrier population in crystalline oxides, which by definition cannot occur in amorphous systems, and provides a framework to discuss key structural descriptors in these disordered phase materials. / Dissertation/Thesis / Doctoral Dissertation Materials Science and Engineering 2020

In der vorliegenden Arbeit wird der reaktive ITO-Abscheidprozess unter Verwendung metallischer In:Sn-Targets eingehend untersucht. Die Schichtabscheidung erfolgt am symmetrisch bipolar gepulstem Dual-Magnetron sowohl auf ruhende als auch bewegte Substrate. Die Arbeit umfasst zwei Teilgebiete. Einerseits wurde der dynamische ITO-Abscheideprozess an einer industrienahen Versuchsanlage umfassend charakterisiert und anhand seiner physikalischen Parameter erfolgreich an eine industrielle Beschichtungsanlage überführt. Andererseits fanden statische Beschichtungen statt. Diese ermöglichen die Analyse der lateralen Verteilung der funktionellen Schichteigenschaften. Dadurch konnte eine Korrelation zu den lateralen Verteilungen der gemessenen Plasmaparameter herausgearbeitet werden.

This work focuses on the development of metal nanowire networks for the use as transparent electrodes in small-molecule organic solar cells. Broad adoption of organic solar cells requires inexpensive roll-to-roll processing on flexible, lightweight substrates. Under these conditions, traditional metal oxide electrodes suffer from significant drawbacks such as brittleness and cost. In contrast, metal nanowire networks provide properties more suitable for high-throughput processing and thus, are investigated here as an alternative. They combine the high-conductivity of metals with the advantage of optical transparency found in aperture-structured networks. The process chain from nanowire deposition to cell integration is examined with silver and copper nanowire material. Two techniques are presented for deposition. While dip-coating is investigated in detail, including a discussion of the most important parameters, spray-coating is demonstrated as an alternative for large area applications. Since the nanowires are barely conductive after deposition, post-treatment steps are used to achieve a performance comparable to standard metal oxide films such as tin-doped indium oxide (ITO). The inherent roughness of nanowire electrodes is addressed by using a conductive polymer as a planarization layer. On top of optimized electrodes, small-molecule organic solar cells are deposited with a UHV thermal evaporation process. Completed cells are tested and performance is found to be comparable to the used standard transparent electrodes. Additionally, a new approach to achieve aligned nanowire network structures is demonstrated. The additional degree of order is used to illustrate optical effects of silver nanowire networks. Furthermore, these aligned networks exhibit anisotropic conductivity. This effect is discussed and simulations are performed to reproduce the observations. The freedom of network design is used to achieve superior conductivity compared to standard random structures. / Im Fokus dieser Arbeit steht die Entwicklung von Metall-Nanodraht-Netzwerken für die Anwendung in transparenten Elektroden für organische Solarzellen. Eine breite Verwendung von organischen Solarzellen setzt eine kostengünstige Rolle-zu-Rolle Fertigung auf flexiblen und leichten Substraten voraus. Unter diesen Bedingungen leiden traditionell verwendete Metalloxid-Elektroden unter erheblichen Nachteilen, wie Brüchigkeit und Preis. Im Gegensatz dazu zeigen Metall-Nanodraht-Netzwerke deutlich bessere Eigenschaften und werden deshalb hier als alternative Elektroden untersucht. Die Netzwerke kombinieren die hohe Leitfähigkeit von Metallen mit einer hohen Transmittivität in Folge der netzwerkbedingten Apertur. Die Prozesskette von der Nanodraht-Abscheidung bis zur Zellintegration wird für Silber- und Kupferdrähte untersucht. Zwei Techniken für die Abscheidung werden präsentiert. Ein Tauchverfahren wird detailliert untersucht und die zugehörigen Parameter werden diskutiert. Für große Flächen wird eine Sprühbeschichtung als Alternative aufgezeigt. Da die abgeschiedenen Netzwerke eine schlechte Leitfähigkeit besitzen, sind Nachprozessierungsschritte notwendig um gute Leitfähigkeiten im Bereich von üblichen Elektroden wie Indium-Zinn-Oxid (ITO) zu erreichen. Die Rauheit der Nanodraht-Elektrode wird mit Hilfe einer glättenden Polymerschicht behoben. Auf den optimierten Elektroden werden organische Solarzellen aus kleinen Molekülen in einem thermischen UHV-Prozess abgeschieden. Die Zellen werden getestet und zeigen Eigenschaften vergleichbar zu üblichen transparenten Elektroden. Zusätzlich wird ein neuer Ansatz zur Herstellung von ausgerichteten Netzwerkstrukturen demonstriert. Der zusätzliche Grad an Ordnung wird für die Untersuchung von optischen Effekten an Silberdraht-Netzwerken genutzt. Weiterhin zeigen diese ausgerichteten Netzwerke eine anisotrope Leitfähigkeit. Dieser Effekt wird diskutiert und Simulationen werden durchgeführt, um die Beobachtungen zu verifizieren. Die Freiheit in der Netzwerkstruktur wird für eine Verbesserung der Leitfähigkeit genutzt.

A key to solar cells with lower environmental impact is higher efficiency and reduced material usages. Bifacial solar cells may have a higher efficiency as light can enter from two directions and tandem solar cells may use a larger part of the incoming solar spectrum, increasing the efficiency. However, both these applications require transparent and conducting contacts. This thesis aimed to investigate how suitable the transparent conductive oxides aluminum doped zinc oxide (AZO) and indium doped tin oxide (ITO) are as contacts in bifacial CIGS cells or CIGS/Silicon tandem cells. The contacts must remain stable when CIGS is deposited on top of it, meaning that they have to endure first 500°C and then 600°C in combination with copper, indium, gallium and selenium vapours. A thin layer of AZO topped with ITO and pure ITO films of different thicknesses were deposited by RF- and DC-sputtering, varying the oxygen flow. Opto-electrical characterization showed that the transparency in the infrared was balanced against high conductivity due to a shift in the plasmon peak's position. No great difference was seen between pure ITO samples and AZO/ITO samples, so only the first where further processed. The ITO films were annealed to 500°C in the CIGS deposition chamber, exposed to selenium vapour. The films' sheet resistances dropped drastically, which was mainly attributed to activation of tin donors. ITO produced with low oxygen flows also appeared more crystalline according to x-ray diffraction measurements. Photon absorption in the ITO was used to estimate the current loss in bifacial and tandem applications and graphs with current loss and sheet resistance can be used to select an ITO deposition process. Commercial ITO was exposed to 100s of the CIGS deposition process but only during selenium and gallium vapour. A layer of gallium selenide could be identified on the surface, but the ITO appeared to remain stable. Sodium fluoride pre deposition treatment lowered the samples absorption for all wavelengths compared to non-treated samples.

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This essay presents a study into the domain of architecture meeting new interaction design principles. The paper discusses future transparent surfaces to become programmable kinetic user interfaces, usable as information and communication channels to simplify our everyday environment. Based on the approach of using the five methodologies: Cultural Probes, Research Through Design, Grounded Theory, Star Life Cycle Model and Wizard of Oz; consistent data was collected to design and iterate on a visionary interface prototype to bridge the use of freehand gestures through motion sensing and moreover supported by RFID in a building structure on a see-through background. The objective of this paper is to unravel the main research question of how can people through kinetic interaction use organic interfaces on transparent surfaces?Several possible uses were ideated such as multiple shared user access, collaborative interaction on both sides. The primary research was answered through a final presented prototype combining a CV system with RFID for multiple and collaborative usages. User experiences and feedback makes an array of applications possible how a transparent interfaces with kinetic interaction can be applied to the interior and exterior such as fridge, mirror, doors, glass panels, alarm systems, games and the home entertainment.In today’s norm screens in the shape of a square are obsolete and support of new patterns, forms and materials are needed. Fieldwork concluded that kinetic interaction could flawlessly unite real world conditions with computer-generated substance, and become the design environment for future interactions to communicate with the user. We no longer seek to be bound to stiff shaped Graphical User Interfaces. Adding a transparent surface as background for such kinetic motion is underlying paradigm for the content to be projected into any ambience and surroundings.

In this project, a cylindrical Luneburg lens isdesigned operating at optical frequencies. A Luneburg lens isa gradient index lens that transforms a point source into aplane wave or vice versa. The lens is rotational symmetric whichallows wide-angle beam scan. In this work, the gradient indexis discretized in layers. The refractive index of each layer isrealized with a transparent liquid. Ray tracing is used to designand evaluate the lens performance. We have simulated Luneburglenses with 4 - 10 layers. Increasing the number of layersimproves the performance. However, difficulties are present inthe manufacturing part of the lens considering that liquids withdesired refractive index cannot be mixed. / I detta projekt designas en cylindrisk Luneburg-lins som fungerar vid optiska frekvenser. En Luneburg-lins är en gradientindexlins som omvandlar en punktkälla till en plan våg eller vice versa. Linsen är rotationssymmetrisk vilket möjliggör vidvinkelstrålescanning. I detta arbete diskretiseras gradienta indexet i lager, brytningsindex för varje lager realiseras med en transparent vätska. Raytracing används för att designa och utvärdera linsprestandan. Vi har simulerat Luneburg-linser med 4 - 10 lager. Genom att öka antalet lager förbättras prestandan. Svårigheter förekommer i linsens tillverkningsprocess med tanke på att vätskor med önskat brytningsindex inte kan blandas. / Kandidatexjobb i elektroteknik 2020, KTH, Stockholm

This dissertation tested the hypothesis that energy transferred from a plasma or plume can be used to optimize the structure, chemistry, topography, optical and electrical properties of pulsed laser deposited and sputtered thin-films of ZnO, a-BOxNy, and few layer 2H-WS2 for transparent electronics devices fabricated without substrate heating or with low substrate heating. Thus, the approach would be compatible with low-temperature, flexible/bendable substrates. Proof of this concept was demonstrated by first optimizing the processing-structure-properties correlations then showing switching from accumulation to inversion in ITO/a-BOxNy/ZnO and ITO/a-BOxNy/2H-WS2 transparent MIS capacitors fabricated using the stated processes. The growth processes involved the optimization of the individual materials followed by growing the multilayer stacks to form MIS structures. ZnO was selected because of its wide bandgap that is transparent over the visible range, WS2 was selected because in few-layer form it is transparent, and a-BOxNy was used as the gate insulator because of its reported atomic smoothness and low dangling bond concentration. The measured semiconductor-insulator interfacial trap properties fall in the range reported in the literature for SiO2/Si MOS structures. X-ray photoelectron spectroscopy (XPS), Hall, photoluminescence, UV-Vis absorption, and X-ray diffraction (XRD) measurements investigated the low-temperature synthesis of ZnO. All films are nanocrystalline with the (002) XRD planes becoming more prominent in films grown with lower RF power or higher pressure. Low power or high chamber pressure during RF magnetron sputtering resulted in a slower growth rate and lower energetic conditions at the substrate. Stoichiometry improved with RF power. The measurements show a decrease in carrier concentration from 6.9×1019 cm-3 to 1.4×1019 cm-3 as power increased from 40 W to 120 W, and an increase in carrier concentration from 2.6×1019 cm-3 to 8.6×1019 cm-3 as the deposition pressure increased from 3 to 9 mTorr. The data indicates that in the range of conditions used, bonding, stoichiometry, and film formation are governed by energy transfer from the plasma to the growing film. XPS characterizations, electrical measurements, and atomic force microscopy (AFM) measurements reveal an increase in oxygen concentration, improved dielectric breakdown, and improved surface topography in a-BOxNy films as deposition pressure increased. The maximum breakdown strength obtained was ~8 MVcm-1, which is comparable to a-BN. Metal-Insulator-Metal (MIM) structures of a-BOxNy grown at 10 and 15 mTorr suggest a combination of field-enhanced Schottky emission and Frenkel-Poole emission are likely transport mechanisms in a-BOxNy. In comparison, better fitted data was gotten for field enhanced Schottky emission which suggests the more dominant mechanism. The static dielectric constant range is 3.26 – 3.58 for 10 and 15 mTorr films. Spectroscopic ellipsometry and UV-Vis spectroscopy measured a bandgap of 3.9 eV for 15 mTorr grown a-BOxNy. 2H-WS2 films were grown on both quartz and a-BOxNy which revealed that the XRD (002) planes became more prominent as substrate temperature increased to 400 oC. AFM shows nano-grains at lower growth pressure. Increasing the growth pressure to 1 Torr resulted in the formation of larger particles. XPS chemical analysis reveals improved sulfur to tungsten ratios as pressure increased. Sulfur deficient films were n-type, whereas sulfur rich conditions produced p-type films. Frequency dependent C-V and G-V measurements revealed an interface trap concentration (Nit) of 7.3×1010 cm-2 and interface state density (Nss) of 7.5×1012 eV-1cm-2 for the transparent ITO/a-BOxNy/ZnO MIS structures, and approximately 2 V was required to switch the a-BOxNy/ZnO interface from accumulation to inversion. Using 2H-WS2 as the channel material, the ITO/a-BOxNy/2H-WS2 required approximately 4 V to switch from inversion to accumulation in both n and p-channel MIS structures. Interface trap concentrations (Nit) of 1.6×1012 cm-2 and 3.2×1010 cm-2, and interface state densities (Nss) of 1.6×1012 eV-1cm-2 and 6.5×1012 eV-1cm-2 were calculated for n and p-channel 2H-WS2 MIS structures, respectively. The data from these studies validate the hypothesis and demonstrate the potential of ZnO, a-BOxNy, and few layer 2H-WS2 for transparent electronics.