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SSAB har som mål till år 2026 att producera fossilfritt stål och vara helt fossilfria vid år 2030. Ett led i att lyckas med detta är att generera egen förnybar elektricitet. I detta arbete utreds på uppdrag av SSAB potentialen för att generera förnybar energi i form av solel på deras industriområde i Borlänge. Denna studie ger även förslag på vilken solcellsteknik som kan utnyttjas, samt hur effekten från solcellsanläggningarna påverkar SSAB:s två största transformatorer. Baslasten för dessa transformatorer kan till stor del uppnås av solcellsanläggningarna mellan april – augusti. De avgränsningar som gjorts syftar till att utreda potentialen av de största ytorna på mark och byggnader inom SSAB:s industriområde. Simuleringar har genomförts med programvaran PVsyst för ett flertal solcellsanläggningar. Arbetet lyfter aspekter om hur solcellsanläggningar fungerar, planeras och påverkas av exempelvis solinstrålning, väder och orientering. Resultatet visar att på de ytor som valdes ut kan en maximal effekt på 28 MWp installeras. Övervägande del av den totala effekten kan installeras på de tillgängliga markytorna, vilket motsvarar ca 70 % av den simulerade installationen. Då de tillgängliga ytorna är riktade åt olika håll kommer de olika föreslagna installationerna att ha sin maximala uteffekt vid olika tillfällen, varför den maximala uteffekten från samtliga anläggningar aldrig överskrider 22 MW. Den totala mängd el som kan genereras från samtliga installationer är 23,7 GWh / år. Denna energimängd motsvarar ca 6 % av SSAB i Borlänges totala elanvändning. Med monokristallina solceller uppgår en kostnad för alla installationerna om 164 miljoner kronor ± 20 %. / SSAB's goal by year 2026 is to produce fossil-free steel and be completely fossil-free by 2030. One step to succeed in this is to generate their own renewable energy. In this work, the authors investigated the potential for generating renewable energy in the form of solar electricity at SSAB’s industrial area in Borlänge. This study also provides suggestions on which solar cell technology can be utilized, as well as how the power from the photovoltaic plants affects SSAB's two largest transformers. The base load of these transformers can mostly be achieved by the photovoltaic plants between April – August. The boundaries made aim to investigate the potential of the largest areas in the form of land and on buildings of the industrial area. Simulations have been carried out with the software PVsyst for several photovoltaic systems. This work highlights aspects of how photovoltaic systems work, how they are planned and affected by, for example, solar radiation, weather and orientation. The simulated photovoltaic systems have different conditions based on the different aspects, where each one has their pros and cons. The result shows that on the surfaces that were selected, a maximum power of 28 MWp can be installed. Most of the total power can be installed on the available land surfaces, which corresponds to about 70 % of the simulated installation. As the available areas are directed in different directions, the proposed installations will have their maximum output at different times, so the maximum output from all plants never exceeds 22 MW. The total amount of electricity that can be generated from all installations is 23.7 GWh / year. This amount of energy corresponds to about 6% of SSAB in Borlänge's total electricity use. With monocrystalline solar cells, a cost for all installations amounts to SEK 164 million ± 20%.

Modern civilization highly depends on energy and finding alternative sources to fossil fuels becomes more and more necessary. The sun is the most abundant energy source available and exploiting it efficiently would result in a great environmental and economic breakthrough. Among the photovoltaic devices, dye-sensitized solar cells (DSCs) emerged for their tremendous commercial potential deriving from a combination of low-cost production and attractive features, such as flexibility and transparency, for indoor and outdoor applications. In the DSCs, a dye anchored to a semiconductor layer (typically TiO2) is responsible for capturing the sunlight and converting it into electricity. Nevertheless, many commercially available dyes for DSCs are based on a very rare metal, ruthenium, and its replacement with a cheaper, more abundant metal is desirable. A good alternative to ruthenium could be copper, which possesses similar photophysical properties in coordination with diimine ligands, but it is considerably cheaper and relatively earth-abundant. In this work, a particular “on-surface self-assembly” strategy was employed to form, on the surface of TiO2, heteroleptic copper (I) complexes with a “push-pull” design which facilitates the electron transfer from the copper (I) complex into the conduction band of TiO2 and enhances the performance of the photovoltaic devices.This thesis focuses on the investigation of the properties of five new heteroleptic copper (I) complexes bearing the same anchoring ligand but different ancillary ligands. Because of the method employed for their synthesis, a solid-state characterization of the optical and electrochemical properties on TiO2 was performed employing tools such as UV-Vis spectroscopy, cyclic voltammetry (CV), and differential pulse voltammetry (DPV). As internal benchmark through the entire characterization, the homoleptic copper (I) complex with the anchoring ligand was also studied. Some patterns between the heteroleptic complexes on TiO2 and their respective homoleptic complexes in solution were found, opening the possibility to predict the behaviour of unknown heteroleptic complexes starting from their corresponding homoleptic. Furthermore, the characterization was necessary to ensure that the complexes were fulfilling the requirements to be employed as dyes. The performances of the heteroleptic, and of the anchoring-ligand homoleptic, copper (I) complexes were then investigated as photosensitizers in DSC devices mainly by measuring the current density-voltage (J-V) characteristics at different light intensities and in the dark, the incident photon-to-current efficiency (IPCE), and electron lifetimes. As benchmark for the degree of effectiveness of the device, the state-of-the-art ruthenium (II) complex N719 was also studied. All the copper (I) complexes showed an overall similar behaviour. The J-V characteristics showed a power conversion efficiency up to 2,05% for the best performing device, which is 25% of the efficiency of DSCs based on N719. On the other hand, the least performing heteroleptic copper (I) complex studied showed an efficiency of 1,23%. From a general analysis combining all the results obtained, it may be concluded that a reason for the limited photocurrent measured through these devices can be due to incomplete dye coverage of TiO2. Despite the lower performance compared to the standard dye N719, the simplicity of the system is promising, and its considerable economic advantage could pave the way to the use of DSCs in everyday life applications. / Modernt samhälle är mycket beroende på energi och det blir allt mer akut att hitta alternativa källor till fossila bränslen. Solen är den mest riklig energikällan som finns och att utnyttja den effektivt skulle resultera i stora miljö- och ekonomiska genombrott. Färgämne sensibiliserade solceller (”dye-sensitized solar cells”; DSC) utvecklade i 90-talet för sin breda kommersiella potential som härrör från en kombination av låg kostnadsproduktion och attraktiva egenskaper, såsom möjligheter för flexibilitet och transparens. I DSC är ett färgämne förankrat till den ytan av en halvledare (vanligtvis TiO2). Färgämnet är ansvarigt för att fånga solljuset och överföra elektronerna till halvledaren för att producera el. Många kommersiella färgämnen för DSC är baserade på rutenium, en mycket sällsynt metall. Ersättning av rutenium med en billigare, rikligmetall är önskvärt mot mer hållbara DSC. En bra alternativmetall till rutenium är koppar. Komplexen av koppar(I) har liknande fotofysiska egenskaper till rutenium (II) men koppar är mer vanlig och mindre dyr än rutenium. Heteroleptiska koppar(I) komplexen med en "push-pull" design syntetiserades på ytan av TiO2 genom "ytan assisterade självmontering". "Push-pull" designen underlättar elektronöverföring från koppar(I)-komplexet till ledningsbandet av TiO2. Denna avhandling fokuseras på undersökning av egenskaperna av fem nya heteroleptiska koppar(I) komplex med den samma förankrings ligand men olika distala ligander. På grund av metoden som används i syntesen av heteroleptiska koppar(I) komplex, var karakterisering av komplexen vid optiska och elektrokemiska metoder utfördes på TiO2. Metoderna för karakterisering var UV-Vis-spektroskopi, cyklisk voltametri (CV) och differentialpuls voltametri (DPV). Som en intern standard genom hela karaktäriseringen studerades även homoleptiska koppar(I) komplex med förankringsliganden. Egenskaperna på heteroleptiska koppar(I) komplexen på TiO2 ytan kunde förutsägas från mätning av egenskaperna på homoleptiska koppar(I) komplexen. Koppar(I) komplexen är undersöktes som fotosensibiliserare i färg-sensibiliserade solceller. Effektiviteten av solcellerna med koppar(I) komplexen eller rutenium (II) komplex (N719) utvärderades genom att mäta fotokurrentdensitetsspänningen (J-V) vid olika ljusintensiteter, incidentfoton-till-ström effektiviteten (”incident photon-to-current efficiency”; IPCE) och laddningsrekombinationen (elektronlivstiden). Koppar(I) komplexen hade övergripande liknande egenskaper i solceller. En kraft omvandlingseffektivitet av 2,05% nås för den bästa solcellen med ett koppar(I) komplex. Medan den bästa effektiviteten med N719 färgämnet var 7,57%. En svaghet i självmonteringen av koppar(I) komplexen på ytan av TiO2 är den ofullständiga bindningen till ytan men självmonteringen metoden var enkel och kunde skapa många, olika färgämnen i kort tid. Trots den lägre prestandan jämfört med standardfärgen N719 är systemets enkelhet lovande, och dess stora ekonomiska fördel kan bana vägen till användningen av DSC i vardagsläget. / La civiltà moderna è fondata sull’uso dell’energia e trovare fonti alternative ai combustibili fossili è diventato sempre più necessario. La radiazione proveniente dal sole è la risorsa energetica più abbondante e disponibile sul nostro pianeta e sfruttarla al massimo comporterebbe una svolta decisiva per l’ambiente e l’economia. Tra i dispositivi fotovoltaici, le celle di Grätzel, conosciute anche come DSC dall’acronimo inglese (dye-sensitized solar cell), sono emerse per il loro enorme potenziale commerciale, dovuto alla combinazione tra basso costo di produzione e interessanti caratteristiche, come la loro flessibilità e trasparenza, che gli conferiscono la possibilità di integrazione negli edifici e l’uso in applicazioni “indoor”. Nelle DSC, un foto-sensibilizzatore, detto anche dye, ancorato ad uno strato di un materiale semiconduttore (tipicamente TiO2), è responsabile della cattura della luce solare e della sua conversione in elettricità. Tra i dye commercialmente disponibili per le DSC vi sono per lo più complessi di coordinazione basati su un metallo molto raro, il rutenio; la sua sostituzione con un metallo più abbondante ed economico è auspicabile per la diffusione di questa tecnologia. Una buona alternativa al rutenio potrebbe essere fornita dal rame, che possiede proprietà foto-fisiche molto simili al primo quando in coordinazione con diimmine; in più è abbastanza economico e relativamente abbondante sulla Terra. Una particolare strategia di "autoassemblaggio sulla superficie" è stata impiegata per formare, sullo strato di TiO2, complessi eterolettici di rame (I) con un design “push-pull” che facilita il trasferimento di elettroni dal complesso di rame (I) alla banda di conduzione di TiO2, migliorando così le prestazioni dei dispositivi fotovoltaici. Questa tesi si concentra sullo studio delle proprietà di cinque nuovi complessi eterolettici di rame (I) che possiedono lo stesso legante di ancoraggio ma diverso legante secondario. A causa del metodo impiegato per la loro sintesi, è stato necessario eseguire la caratterizzazione delle loro proprietà ottiche ed elettrochimiche direttamente sulla superficie del TiO2, utilizzando strumenti come la spettroscopia UV-Visibile, la voltammetria ciclica (CV) e la voltammetria ad impulsi differenziali (DPV). Come riferimento interno durante l'intera caratterizzazione, è stato studiato anche il complesso di rame (I) omolettico con il legante di ancoraggio. Tra i complessi eterolettici su TiO2 e i loro rispettivi complessi omolettici in soluzione, è stato individuato un trend con la possibilità di prevedere il comportamento dei primi a partire dal loro corrispondente omolettico. Inoltre, la caratterizzazione ottica ed elettrochimica è necessaria per garantire l’adeguatezza dei complessi come dye. Le prestazioni dei complessi eterolettici e del complesso omolettico con il legante di ancoraggio, sono state quindi studiate come foto-sensibilizzatori nei dispositivi DSC; in particolare è stata misurata la curva di densità di corrente – voltaggio (J-V) a diverse intensità di luce e al buio, l’efficienza quantica esterna (EQE o dall’acronimo inglese incident photon-to-current efficiency, IPCE) e infine il tempo di vita dell’elettrone nella banda di conduzione del semiconduttore. Come standard interno, per verificare l’efficacia del dispositivo, è stato anche studiato il ben noto complesso di rutenio (II), N719. Generalmente, tutti i complessi di rame (I) hanno mostrato un comportamento simile. Le curve caratteristiche J-V hanno presentato un'efficienza pari fino al 2,05% per il complesso di rame che ha dato le prestazioni migliori (25% dell'efficienza di N719). Da un'analisi generale che combina tutti i risultati ottenuti, si può concludere che una ragione per cui la foto-corrente risulta limitata potrebbe essere data dall’incompleta copertura del TiO2 da parte del complesso di rame (I) e quindi dallo scarso adsorbimento del dye. Nonostante le prestazioni inferiori rispetto allo standard N719, la semplicità del sistema è promettente e il suo notevole vantaggio economico potrebbe aprire la strada all'utilizzo delle DSC nelle applicazioni della vita quotidiana.

Conjugated polymer architecture and morphology are two of the key factors that determine corresponding opto-electronic device performance. It is well-known that conjugated polymers display a variety of conformations and exhibit aggregation in their materials and even for individual polymer chains. The intrinsic structural heterogeneity of conjugated polymers strongly complicates the active layer morphology and phase separation, which are crucial for photoinduced charge generation and transport in polymer based bulk heterojunction-organic photovoltaics device (BHJ-OPVs). Aiming to probe the molecular level correlations between conjugated polymer architecture, morphology and optoelectronic properties, single molecule spectroscopy (SMS) and single particle spectroscopy (SPS) were employed. The molecular level folding properties of conjugated polymers were studied and correlated to the chemical architecture and rigidness of the polymer backbones by means of SMS and single molecule polarization anisotropy imaging. First, a block copolymer consisting of poly(3-hexylthiophene) (P3HT) and (60)fullerene (C₆₀) was investigated due to its potential for forming active layers in OPV devices that exhibit long-term phase stability and efficient exciton dissociation into free charge carriers. It was demonstrated that the grafting of the C₆₀-containing block does not significantly affect the conformation of the backbone of the P3HT block. Next, a series of thiophene based polymers showing different macroscale crystallization behavior were investigated. The rigidness of the conjugated polymer backbones was found to be correlated with the chemical architecture of the molecules. However, even the polymers that show no folding in their respective crystals and are thus expected to be the most rigid, still exhibit folding at the single molecule level. From this work it is clear that besides chemical architecture, intermolecular interactions in the crystal structure also need to be considered. For conjugated polymer materials, in this dissertation specifically the blends of conjugated polymers with fullerenes as found in the active layer of OPVs, the investigation of the molecular level correlations between conjugated polymer architecture, morphology and optoelectronic properties can be prohibitively complex due to the presence of a large number of molecules. Furthermore, in the research presented herein, as well as in the literature, it has been clearly shown that the polymer molecules themselves exhibit severe heterogeneity in their properties (chain morphology, aggregation, optical and electronic properties). Therefore, in order to simplify the structure-property investigations concerning nanodomains in BHJ-OPVs, we developed P3HT/PC₆₀BM (PC₆₀BM: (6,6)-phenyl-C₆₁-butyric acid methyl ester) composite nanoparticles (NPs). The size of the nanoparticles corresponds with a few polymer and fullerene domains when considering a similarly sized volume in the active layer of OPVs. Single particle spectroscopy combined with this unique nanoparticle material system reveals variations in molecular conformation and aggregation of the conjugated polymer chains upon doping with different weight percentages of fullerene. These newly developed NPs were embedded in a hole-injection device to study the exciton-hole polaron interactions and the charge transfer processes at the interface between a hole-transporting layer and the NPs. Pronounced charge trapping was observed for donor-acceptor blend NPs due to the large amount of photogenerated free charge carriers. Besides fundamental studies on morphology-property relations for thiophene based conjugated polymers, fabrication of BHJ-OPVs based on P3HT and PC₆₀BM was also completed. Low band gap polymer PTB-7 (poly((4,8-bis((2-ethylhexyl)oxy)benzo (1,2-b:4,5-b')dithiophene-2,6-diyl)(3-fluoro-2-((2-ethylhexyl)carbonyl)thieno(3,4-b) thiophenediyl))) and a near-infrared (NIR) small dye molecule were incorporated into active layers of these P3HT/PC₆₀BM BHJ-OPVs to expand the photoresponse of the devices. The effects of doping the P3HT/PC₆₀BM BHJ-OPVs with PTB-7 and NIR dye on the device performance and film morphology were investigated. The doping of PTB-7 can efficiently extend the photoresponse of the resultant devices into the NIR regime and improve the device performance with respect to the reference (undoped) devices, demonstrating an elegant and pragmatic approach in improving light-harvesting efficiency in BHJ-OPVs.

Functional oxides are versatile materials that can simultaneously enable efficiency gains and cost reductions in crystalline silicon (c-Si) solar cells. In this work, the deposition of functional oxide materials using atmospheric pressure chemical vapor deposition (APCVD) and the integration of these materials into c-Si solar cells are explored. Specifically, thin oxide films and multi-layer film stacks are utilized for the following purposes: (1) to minimize front surface reflectance without increasing parasitic absorption within the anti-reflection coating(s); (2) to maximize internal back reflectance of rear passivated cells, thereby increasing optical absorption of weakly absorbed long wavelength photons (? > 900 nm); (3) to minimize recombination losses by providing excellent surface passivation; and (4) to improve doping processes during cell manufacturing (e.g., emitter and surface field formation) by functioning as highly controllable dopant sources compatible with in-line diffusion processes. The oxide materials deposited by APCVD include amorphous and polycrystalline titanium oxide, aluminum oxide, boron-doped aluminum oxide, silicon oxide, phosphosilicate glass, and borosilicate glass. The microstructure, optical properties, and electronic properties of these films are characterized for different deposition conditions. Additionally, the impact of these materials on the performance of different types of c-Si solar cells is presented using both simulated and experimental current-voltage curves.

The main objective of this research was to develop efficient CuIn1-xGaxS2 (CIGS2)/CdS thin film solar cells for photoelectrochemical (PEC) water splitting to produce very pure hydrogen and oxygen. Efficiencies obtained using CIGS2 have been lower than those achieved using CuInSe2 and CuIn1-xGaxSe2. The basic limitation in the efficiencies is attributed to lower open circuit voltages with respect to the bandgap of the material. Presently, the main mechanism used to increase the open circuit voltage of these copper chalcopyrites (CuInSe2 and CuInS2) is the addition of gallium. However, addition of gallium has its own challenges. This research was intended to (i) elucidate the advantages and disadvantages of gallium addition, (ii) provide an alternative technique to the photovoltaic (PV) community to increase the open circuit voltage which is independent of gallium additions, (iii) develop highly efficient CIGS2/CdS thin film solar cells and (iv) provide an alternative material in the form of CIGS2/CdS thin film solar cells and an advanced technology in the form of a multiple bandgap tandem for PEC water splitting. High gallium content was achieved by the incorporation of a highly excess copper composition. Attempts to achieve high gallium content produced reasonable but not the best solar cell performance. Few solar cells developed on a molybdenum back contact and an ITO/MoS2 transparent conducting back contact showed a PV conversion efficiency of 7.93% and 5.97%, respectively. The solar cells developed on the ITO/MoS2 back contact form the first generation CIGS2/CdS thin film solar cells and 5.97% is the first ever reported efficiency on an ITO/MoS2 transparent back contact. Reasons for the moderate performance of these solar cells were attributed to significant porosity and remnants of unsulfurized CuGa alloy in the bulk of CIGS2. This was the first attempt to a detailed study of materials and device characteristics of CIGS2/CdS thin film solar cells prepared starting with a highly excess copper content CIGS2 layer. Next, excess copper composition of 1.4 (equivalent to gallium content, x = 0.3) was chosen with the aim to achieve the best efficiency. The open circuit voltage was enhanced by depositing an intermediate layer of intrinsic ZnO between CdS and ZnO:Al layers. The systematic study of requirements for such a layer and further optimization of its thickness to achieve a higher open circuit voltage (which is the greatest challenge of the scientific community) forms an important scientific contribution of this research. The PV parameters for CIGS2/CdS thin film solar cell as measured officially at the National Renewable Energy Laboratory were: open circuit voltage of 830.5 mV, short circuit current density of 21.88 mA/cm2, fill factor of 69.13% and photovoltaic conversion efficiency of 11.99% which sets a new world record for CIGS2 cells developed using sulfurization and the open circuit voltage of 830.5 mV has become the "Voc champion value". New PEC setups with the RuS2 and Ru0.99Fe0.01S2 photoanodes were developed. RuS2 and Ru0.99Fe0.01S2 photoanodes were more stable in the electrolyte and showed better I-V characteristics than the RuO2 anode earlier used. Using two CIGS2/CdS thin film solar cells, a PEC efficiency of 8.78% was achieved with a RuS2 anode and a platinum cathode. Results of this research constitute a significant advance towards achieving practical feasibility and industrially viability of the technology of PEC hydrogen generation by water splitting.

High efficiency CuIn1-xGaxSe2-ySy (CIGSS)/CdS thin-film solar cells were prepared by optimizing the Mo back contact layer and optimizing the parameters for preparing CIGSS absorber layer using diethylselenide as selenium source. The Mo film was sputter deposited on 2.5 cm x 10 cm soda-lime glass using DC magnetron sputtering for studying the adhesion and chemical reactivity with selenium and sulfur containing gas at maximum film growth temperature. Mo being a refractory material develops stresses, nature of which depends on the deposition power and argon pressure. It was found that the deposition sequence with two tensile stressed layers deposited at 200W and 5 x 10-3 Torr argon pressure when sandwiched between three compressively stressed layers deposited at 300 W power and 0.3 x 10-3 Torr argon pressure had the best adhesion, limited reactivity and compact nature. An organo-metallic compound, diethylselenide (DESe) was developed as selenium precursor to prepare CIGSS absorber layers. Metallic precursors Cu-In-Ga layers were annealing in the conventional furnace in the temperature range of 475oC to 515 oC and in the presence of a dilute DESe atmosphere. The films were grown in an indium rich regime. Systematic approaches lead to the optimization of each step involved in the preparation of the absorber layer. Initial experiments were focused on obtaining the range of maximum temperatures required for the growth of the film. The following experiments included optimization of soaking time at maximum temperature, quantity of metallic precursor, and amount of sodium in terms of NaF layer thickness required for selenization. The absorber surface was coated with a 50 to 60 nm thick layer of CdS as hetero-junction partner by chemical bath deposition. A window bi-layer of i:ZnO/ZnO:Al was deposited by RF magnetron sputtering. The thickness of i:ZnO was increased to reduce the shunt resistance to improve open circuit voltage. The cells were completed by depositing a Cr/Ag front contact by thermal evaporation. Efficiencies greater than 13% was achieved on glass substrates. The performance of the cells was co-related with the material properties.

Thin-film solar cells are potentially low-cost devices to convert sunlight into electricity. Improvements in the conversion efficiencies of these cells reduce material utilization cost and make it commercially viable. Solar cells from the Thin-Film Physics Group, ETH Zurich, Switzerland and the Florida Solar Energy Center (FSEC), UCF were characterized for defects and other microstructural features within the thin-film structure and at the interfaces using transmission electron microscopy (TEM). The present thesis aims to provide a feedback to these groups on their deposition processes to understand the correlations between processing, resulting microstructures, and the conversion efficiencies of these devices. Also, an optical equipment measuring photocurrents from a solar cell was developed for the identification of defect-prone regions of a thin-film solar cell. The focused ion beam (FIB) technique was used to prepare TEM samples. Bright-field TEM along with scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDS) including elemental distribution line scans and maps were extensively used for characterizing the absorber layer and interfaces both above and below the absorber layer. Energy-filtered transmission electron microscopy (EFTEM) was applied in cases where EDS results were inconclusive due to the overlap of X-ray energies of certain elements, especially molybdenum and sulfur. Samples from ETH Zurich were characterized for changes in the CIGS (Cu(In,Ga)Se2) microstructure due to sodium incorporation from soda-lime glass or from a post-deposition treatment with NaF as a function of CIGS deposition temperature. The CIGS-CdS interface becomes smoother and the small columnar CIGS grains close to the Mo back contact disappear with increasing CIGS deposition temperature. At 773 K the two sodium incorporation routes result in large differences in the microstructures with a significantly larger grain size for the samples after post-deposition Na incorporation. Porosity was observed in the absorber layer close to the back contact in the samples from FSEC. The reason for porosity could be materials evaporation in the gallium beam of the FIB or a processing effect. The porosity certainly indicates heterogeneities of the composition of the absorber layer near the back contact. A Mo-Se rich layer (possibly MoSe2) was formed at the interface between CIGS/CIGSS and Mo improving the quality of the junction. Other chemical heterogeneities include un-sulfurized Cu-Ga deposits, residual Se from the selenization/ sulfurization chamber in CIGS2 and the formation of Cu-rich regions which are attributed to decomposition effects in the Ga beam of the FIB. Wavy absorber surfaces were observed for some of the cells with occasional discontinuities in the metal grids. The 50 nm thick CdS layer, however, remained continuous in all the samples under investigation. For a sample with a transparent back contact, a 10 nm Mo layer was deposited on ITO (indium tin oxide) before deposition of the CIGS2 (Cu(In,Ga)S2) layer. EFTEM maps indicate that a MoS2 layer does not form for such a Mo/MoS2-ITO back contact. Instead, absorber layer material diffuses through the thin Mo layer onto the ITO forming two layers of CIGS2 on either side of Mo with different compositions. Furthermore, an optical beam induced current (OBIC) system with micron level resolution was successfully developed and preliminary photocurrent maps were acquired to microscopically identify regions within a thin-film solar cell with undesirable microstructural features. Such a system, when fully operational, will provide the means for the identification of special regions from where samples for TEM analysis can be obtained using the FIB technique to study specifically the defects responsible for local variations in solar cell properties.