Master of Science (MS), Bowling Green State University, 2014, Physics

Third generation quantum dot solar cells are one of the promising sources of clean energy. However, poor eciency is a major issue; they are in a positive direction of optimization. To optimize their performance, we should select the materials which can absorb more light radiation in visible and infrared regions. To this regard, the gold plasmonic enhancement shows a promise to improve the eciency of photovoltaics. Here, we report a solution process of depleted heterojunction PbS solar cells in the presence of gold nanoparticles. In our experiment, the solar cells show a better absorption and eciency in the presence of the Au nanoparticles. The fabricated solar cell in the addition of Au nanoparticles has the average efficiency of 4.15%, where as the solar cell without plasmons has the average effieciency of 4.00%.

Committee: Mikhail Zamkov (Advisor); Haowen Xi (Committee Member); Alexey Zayak (Committee Member) Subjects: Physics

Master of Science, University of Akron, 2023, Polymer Science

In the realm of perovskite solar cells, there has been a substantial rise in research focusing on organic-inorganic halide perovskites (OIHPs) in recent years. This is owing to remarkable progress in single junction OIHPs' power conversion efficiency (PCE), which has improved from 3.8% in the initial prototype built in 2009 to a current state-of-the-art value of approaching 26%. However, the weak bonding of the organic components in the hybrid crystal structure has made the OIHPs chemically unstable and susceptible to degradation caused by humidity, ultraviolet light, and heat. This is a major challenge that must be addressed for them to be suitable for industrial-scale production. In response to this challenge, alternative materials, such as inorganic cesium-based metal halide perovskites (CsPbX3, X = I, Br, or mixed), have attracted significant interest. These materials have shown great promise in terms of their power conversion efficiency (PCE), with some achieving PCE values exceeding 20%. Among these inorganic materials, CsPbI2Br stands out as a promising candidate due to its suitable bandgap and stable phase under operation conditions. However, the significant voltage deficit in inorganic CsPbI2Br-based PSCs, particularly in the inverted structure, remains a challenge for further PCE enhancement. This study presents a simple and effective approach to improve the performance of inverted all-inorganic CsPbI2Br-based PSCs by leveraging unreacted metal halide (PbI2) to passivate grain boundaries in the bulk perovskite film. The CsPbI2Br solar cells with an optimized excess of PbI2 exhibit reduced voltage deficits, boosting the open-circuit voltage from 1.04 V to 1.18 V, resulting in a PCE of 13.19% for inverted CsPbI2Br PSCs. Furthermore, the devices demonstrate improved long-term and thermal stability compared to the pristine devices. This approach holds promise for the development of inorganic perovskite solar cells with superior performance and stability, circu (open full item for complete abstract)

Committee: Mark Soucek (Advisor); Xiong Gong (Committee Member) Subjects: Chemistry; Condensed Matter Physics; Electrical Engineering; Engineering; Nanotechnology; Physics; Solid State Physics

Doctor of Philosophy, Case Western Reserve University, 2014, Chemistry

Organic photovoltaic is a promising technology for solar energy harvesting. The power conversion efficiency (PCE) of solution-processed bulk heterojunction (BHJ) cells has reached over ~10%. Fullerene and its derivatives have been the most investigated acceptor. However, fullerene derivatives have disadvantages: (i) weak absorption in visible and near-IR range, (ii) limited energy tunability. Promising alternative non-fullerene acceptors are limited, and the best efficiency achieved so far is ~5%. In this study, we used azadipyrromethene (ADP) as the building block to synthesize a series of electron acceptors. ADP derivatives are strong chromophores with strong absorption around ~ 600 nm. They are electro-active materials with two reduction peaks. Their optoelectronic properties can be tuned upon structural modifications. In this work, we synthesized a series of 3-dimensional (3D) conjugated homoleptic Zn(II) complexes of ADP dyes. The degree of conjugation in ADP was extended by installing phenylacetylene, ethynylthiophene and thiophene groups at the pyrrolic positions of the ADP core using Stille coupling. 3D structures of these molecules were synthesized by chelating with Zn(II). These new molecules showed broad intense red to near-IR absorption with onsets around 800 nm. The estimated LUMO energy level of Zn(II) complexes ranged from -3.60 to -3.85 eV. Their strong acceptor properties were demonstrated by fluorescence quenching experiments using poly(3-hexylthiophene) as the donor. These metal complexes quenched the fluorescence efficiently in both solutions and film. DFT calculations showed that all the metal complexes have distorted tetrahedral structures, with additional conjugated `arms' extending in 3 dimensions. A unique feature of these complexes is that the two ADP ligands are p-stacked with each other, with frontier molecular orbitals delocalized over the two ligands. These complexes can therefore easily accept electrons, delocalize the negative char (open full item for complete abstract)

Committee: Geneviève Sauvé (Advisor); Anna Samia (Committee Chair); Clemens Burda (Committee Member); Robert Dunbar (Committee Member) Subjects: Alternative Energy; Chemistry; Energy; Molecular Chemistry; Molecular Physics; Molecules; Morphology; Organic Chemistry; Physical Chemistry

Doctor of Philosophy in Engineering, University of Toledo, 2005, Electrical Engineering

This dissertation provides the first detailed description of the fabrication of flexible, monolithically interconnected photovoltaic sub-modules based on triple-junction amorphous silicon (a-Si) cell technology. There are several problems encountered when progressing from small area (0.25 cm²) solar cells to series interconnected modules that are three orders of magnitude larger in area. This work involved the development of techniques required to overcome some of those problems, and the application of these in order to successfully fabricate triple-junction a-Si based solar sub-modules 10 cm x 30 cm (4"x12") in size. The solar cells were fabricated on Kapton-VN and Upilex-S polyimide films. Polyimide films were chosen because polyimides have the highest thermal and dimensional stability of any polymer commercially available in film form. Chromium or molybdenum tie-coat layers were introduced between the polyimide and back-reflector films in order to improve film adhesion, which is otherwise unsatisfactory. An improved electrochemical shunt passivation process (light assisted shunt passivation) was developed and used to passivate shunts in the cells. Shunt passivation is especially important for larger area solar cells. A combination of laser (dry) and wet chemical processing was used for the series interconnection. A laser-weld based interconnection scheme was chosen, for its compatibility with the shunt passivation process. The cells were encapsulated with the terpolymer THV (St. Gobain) and Tefzel (Dupont), using a vacuum laminator that was specially built for this purpose. To summarize, triple-junction-amorphous-silicon-based, series interconnected photovoltaic submodules of size 10 cm x 30 cm were fabricated on lightweight and flexible substrates. The modules have an aperture area of approximately 200 cm2. An initial AM1.5 efficiency of 4.75% (5.34% in natural sunlight) was obtained for a module with an aperture area of 204 cm². The specific power of this modul (open full item for complete abstract)

Committee: Xunming Deng (Advisor) Subjects:

Doctor of Philosophy, The Ohio State University, 2021, Electrical and Computer Engineering

The solar energy industry has been growing rapidly due to decreasing costs of manufacturing and increasing panel efficiencies. As the industry dominant crystalline Si solar cell technology approaches its fundamental efficiency limits, new strategies for achieving higher efficiency while maintaining low cost is a necessity to continue the industries growth. The only demonstrated way to surpass the fundamental single junction efficiency barrier is through the use of multijunction photovoltaic cells. The multijunction cell architecture splits the solar spectrum to be absorbed by two or more different semiconductor materials with the highest energy photons being absorbed by the wider bandgap top cells, and lower energy light being absorbed by the narrower band gap bottom cells. This technology has been very successfully demonstrated in the III-V materials system and scaled by the space solar industry; however, terrestrial power generation has much stricter requirements on production cost than the space solar industry. Thus, arises the potential for an interesting marriage of technologies. Imagine combining the highly scaled Si manufacturing infrastructure, the low-cost Si wafer materials, and high efficiency III-V multijunction cells. This is the precise combination present in III-V/Si tandem solar cells. To date, two fabrication methods, mechanical stacking and surface activated wafer bonding, have demonstrated impressive 3-junction solar cells with efficiencies of 35.9%[1] and 34.1%[2] respectively. The issue is that these techniques are not largely considered scalable for terrestrial scale power generation; however, these prototype devices demonstrate great promise for this III-V/Si device architecture. The most scalable method of III-V/Si integration is through the use of epitaxy to monolithically integrate the III-V and Si solar cells; however, this approach can lead to defect formation due to differences in the lattice parameter, crystal structure, and th (open full item for complete abstract)

Committee: Steven Ringel (Advisor); Tyler Grassman (Advisor); Sanjay Krishna (Committee Member) Subjects: Electrical Engineering; Energy; Engineering

Doctor of Philosophy, University of Toledo, 2020, Physics

Photovoltaic (PV) solar cells have attracted great attention because of the demand for low cost renewable energy sources. Detailed information on electronic properties, such as doping, defects, gap states…etc, must be fully understood to develop the technology of solar cells. Here, we report the fundamental electronic properties of two distinct materials systems, one is based on polycrystalline cadmium telluride (CdTe) and the other is lead-halide perovskite solar cells. This investigation provides useful information to understand the fundamental nature of single junction solar cell device and material. First, we investigate the impact of back surface treatment method for cadmium sulfide (CdS)/CdTe solar cells using hydroiodic acid (HI) etching to provide an appropriate electrical back contact. The structural properties of CdTe films and electrical properties of the CdTe absorber and interfaces are characterized. Using capacitance-based techniques with the support of current–voltage measurements, we show that the barrier height of the back contact is reduced, apparent doping concentration is increased, and a defect level at 0.409eV is eliminated after the HI-treatment. More importantly, the CdTe device performance is improved. This improvement is still limited by many factors. One factor is the device window layer that limits the current generation. Therefore, we replaced CdS layer by wide bandgap material, ZnMgO (ZMO). We noticed that the electrical properties of CdS/CdTe and ZMO/CdTe solar cells depend on both buffer material and the fabrication atmosphere. Using capacitance spectroscopy-based techniques, we show that CdS/CdTe solar cells have negligible front contact barriers regardless of the fabrication atmospher, while ZMO/CdTe devices show obvious front barriers are dependent on the fabrication atmosphere. Both CdS/CdTe and ZMO/CdTe solar cells have significant back contact barriers. Additionally, we find that the energy level of defects in CdS/CdTe cells (open full item for complete abstract)

Committee: Yanfa Yan (Committee Chair); Jian Li (Committee Member); Jacques Amar (Committee Member); Xunming Deng (Committee Member); Nikolas Podraza (Committee Member) Subjects: Energy; Materials Science; Physics

Doctor of Philosophy, The Ohio State University, 1982, Graduate School

Committee: Not Provided (Other) Subjects: Chemistry

Master of Science, The Ohio State University, 2016, Chemistry

Solar energy has become an important component in the clean energy mix. There are several different kinds of solar cells that have been developed over decades. The focus of the first three chapters will be p-type dye-sensitized solar cells (DSSCs), which are omnipotent for obtaining high efficiency and cost effective tandem DSSCs. The efficiency of p-type DSSCs lags behind their n-type counterpart due to being less investigated. Herein, the attempts to increase performance of the p-type component via molecular engineering of organic photosensitizers is described. Through the addition of bulky hydrophobic alkyl chains performance can be enhanced, though it was found that the location of these alkyl chains is a critical factor. Additionally, by adopting a double-acceptor single-donor design, as described in chapter 3, when employing the commonly used triphenylamine donor moiety, one can simultaneously increase the molar extinction coefficient while reducing the synthetic steps yielding one the fields top performing photosensitzers. In addition to the conversion of solar energy to electrical energy, the storage of intermittent renewable energy is important. Energy can be stored mechanically (e.g. pumped hydro, fly wheels, compressed air, etc.), electrochemically (e.g. batteries and capacitors), or in chemical bonds (e.g. hydrolysis, carbon dioxide reduction, etc.). Of these methods hydrolysis to produce hydrogen has been identified as an attractive potential method. This is because hydrogen has high specific energy, can be transported, and used as a fuel in fuel cells emitting only water. The problem is industry currently employs steam-methane reforming to produce hydrogen, because catalysts currently employed for hydrolysis are expensive (i.e. noble metals) and/or unstable. Therefore finding a more abundant, lower cost, and stable catalyst which can be easily processed has been of importance. Molybdenum disulfide based catalysts have been identified as a good cand (open full item for complete abstract)

Committee: Yiying Wu PhD (Advisor); James Cowan PhD (Committee Member) Subjects: Chemistry; Energy; Gases; Organic Chemistry; Polymer Chemistry; Polymers

Doctor of Philosophy, University of Toledo, 2010, Physics

The multilayer optical structure of thin film polycrystalline II-VI solar cells such as CdTe is of interest because it provides insights into the quantum efficiency as well as the optical losses that limit the short-circuit current. The optical structure may also correlate with preparation conditions, and such correlations may assist in process optimization. A powerful probe of optical structure is real time spectroscopic ellipsometry (SE) that can be performed during the deposition of each layer of the solar cell. In the CdCl2 post-deposition treatment process used for thin film polycrystalline II-VI solar cells, the optical properties of each layer of the cell change during the process due to annealing as well as to the elevated temperature. In this case, ex-situ SE before and after treatment becomes a reasonable option to determine the optical structure of CdCl2-treated CdTe thin film solar cells. CdTe solar cells pose considerable challenges for analysis by ex-situ SE. First, the relatively large thickness of the as-deposited CdTe layer leads to considerable surface roughness, and the CdCl2 post-deposition treatment generates significant additional oxidation and surface inhomogeneity. Thus, ex-situ SE measurements in reflection from the free CdTe surface before and after treatment can be very difficult. Second, SE from the glass side of the cell is adversely affected by the top glass surface which generates a reflection that is incoherent with respect to the reflected beams from the thin film interfaces and consequently depolarization if collected along with these other beams. In this research, the first problem is solved through the use of a succession of Br2+methanol treatments that smoothens the CdTe free surface, and the second problem is solved through the use of a 60° prism optically-contacted to the top glass surface that eliminates the top surface reflection. In addition, the succession of a Br2+methanol treatment not only smoothens the CdTe surface but (open full item for complete abstract)

Committee: Robert W. Collins PhD (Committee Chair); Alvin D. Compaan PhD (Committee Member); Dean M. Giolando PhD (Committee Member); Randy Ellingson PhD (Committee Member); Thomas J. Kvale PhD (Committee Member) Subjects: Physics

Master of Science, Miami University, 2009, Paper Science and Engineering

This thesis focuses on four different aspects. 1) Use hybrid TiO2 electrode instead of doctor bladed TiO2 for dye sensitized solar cells (DSSCs) and observed an increase in efficiency from 1.6% to 2.11%. 2) We investigated the post annealing treatment on the CdS sensitized ZnO and TiO2 nanocrystalline solar cells. It was found that the annealing will increase the cell efficiency on ZnO and TiO2 with porous structures. 3) We studied the degradation mechanism using damp heat based on ZnO and Al:ZnO. We found that the Al dopant would enhance the moisture capture ability in ZnO, causing degradation under damp heat and annealing treatment.4) we have compared the differences between Zn1-xMgxO and Al: Zn1-xMgxO and concluded that the existing of Al in the film would vary the film performance.

Committee: Dr.Lei Kerr PhD (Advisor); Dr. Shashi Lalvani PhD (Committee Member); Dr.Coffin Douglas PhD (Committee Member); Dr.Catherine Almquist PhD (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy, Case Western Reserve University, 2014, Chemistry

Core-substituted naphthalenediimides (core-substituted NDIs) were incorporated into rod-like molecules and oligomers through reaction at the imide nitrogen positions. N,N'-Di(4-bromophenyl)-2,6-di(N-alkylamino)-1,4,5,8-naphthalenetetracarboxydiimide was synthesized in only three steps, and used as a versatile platform to prepare extended structures by reaction with thiophene substrates using Suzuki-coupling conditions. The optoelectronic properties of the new compounds were examined by UV/vis absorption spectroscopy, fluorescence spectroscopy, cyclic voltammetry and theoretical calculations. The imide substituents had little effect on the optical and electrochemical properties of core-substituted NDIs in solution. A bathochromic shift of the absorption was observed upon film formation, accompanied by quenching of fluorescence. These observations are consistent with increased inter-molecular interactions between core-substituted NDI moieties in the solid state. All compounds were tested in organic solar cells by blending with poly(3-hexylthiophene) (P3HT), and several showed a photovoltaic effect, demonstrating their potential as electron acceptors in organic solar cell. The best solar cell was observed for core-substituted NDI with 4-(thiophen-2-yl)phenyl imide substituents (5a), showing a power conversion efficiency of 0.57% and a large open circuit voltage of 0.87 V. This approach allows new structure-property relationship studies of non-fullerene acceptors in organic solar cells, where one can vary the imide substituent to optimize photovoltaic parameters while keeping the optical and electrochemical properties constant. To study the structure-property relationships of core-substituted NDIs as acceptors for organic solar cells, a series of 2,6-dialkylamino NDI compounds with various substituents were synthesized, characterized and tested in bulk heterojunction solar cells by blending with P3HT. The imide substituents consisted of a linker connected to a thioph (open full item for complete abstract)

Committee: Geneviève Sauvé (Advisor); John Protasiewicz (Committee Chair); Thomas Gray (Committee Member); Carlos Crespo (Committee Member) Subjects: Alternative Energy; Chemistry; Energy; Materials Science; Molecular Chemistry; Molecules; Morphology; Organic Chemistry; Physical Chemistry

Doctor of Philosophy, University of Akron, 2024, Polymer Engineering

The increased use of solar energy for power is anticipated to lead to the shift from traditional power sources to renewable energy sources. Photovoltaic (PV) is a promising technology due to its ability to directly convert sunlight into electricity with no pollution. Solar cells, specifically those based on metal halide perovskites (MHPs) have gained popularity recently due to their power conversion efficiency (PCE) that have increased dramatically over the past 15 years, from 3.8% to more than 26 %. The rapid development in PCE is due to the advanced features that MHPs have such as cost-effective and easy processing, high absorption coefficient, large diffusion length, and low exciton binding energy. In particular, the purpose of this study is to develop solution-processed perovskite solar cells (PSCs) by tuning film morphology and optoelectronic properties of metal halide perovskites incorporated with processing additives, thereby optimizing the performance of PSCs. To maximize the potential of perovskite, controllable crystallization is crucial for producing high-quality perovskite thin films with fewer structural defects and additive engineering is a facile and effective method among other techniques. We mainly investigated the effects of various processing additives on the MHPs based on MAPbI3 perovskite (where MA is CH3NH3) and correlate PCE in term of film morphology, crystallinity, photocurrent hysteresis, optoelectronic properties, device performance and stability of PSCs.

Committee: Xiong Gong (Advisor); Fardin Khabaz (Committee Chair); Mark D. Soucek (Committee Member); Mesfin Tsige (Committee Member); Jie Zheng (Committee Member) Subjects: Energy; Engineering; Materials Science; Nanotechnology

Master of Science, The Ohio State University, 2005, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science (MS), Bowling Green State University, 2024, Physics

Thin film photovoltaic (PV) devices have improved power conversion efficiency over the last few decades, but much improvement is still needed. One challenge is determining where the most significant loss of efficiency occurs. The presence of band tails, which are the density of states of the energy levels that extend into the bandgap of a semiconductor, reduces the efficiency of PV devices. They are caused by disorders in the material and fluctuations in the band gap. These band tails affect charge transport, photon absorption, and recombination mechanisms. Band tails are mainly studied using photoluminescence (PL). This research includes PV device simulations incorporating band-tail physics with a generalized band-tail model and experimental data from the National Renewable Energy Laboratory (NREL). The inputs into the device simulations are derived from general PL models or PL data. Specifically, this work focuses on Cd(Se,Te) devices, but the approach is generally applicable to any PV technology. By modeling a broad parameter space of band tail characteristics, simulations show a decrease in the open-circuit voltage (Voc) and the power conversion efficiency the further the band tails go into the band gap. This is consistent between experimental data and numerical modeling. Key findings indicate that band tails cause a red-shift in the photoluminescence (PL) peak, reduce the Voc, and are influenced by nonuniform impurities like selenium and arsenic. Band tails also limit the practical performance and efficiency of modern devices. The research will continue expanding our understanding of the connections between band tails and PV device performance.

Committee: Marco Nardone Ph.D. (Committee Chair); Mikhail Zamkov Ph.D. (Committee Member); Andrew Layden Ph.D. (Committee Member) Subjects: Physics

Master of Science (M.S.), University of Dayton, 2024, Chemical Engineering

There is a continuous thrust for cleaner and more sustainable alternatives for energy conversion with the increasing global energy demand. Among them, photovoltaics, specifically thin film solar cells are highly promising and are one of the fastest growing clean energy technologies in the United States. This research presents the synthesis and characterization of a set of novel multinary copper chalcogenide semiconductor nanocrystals (NCs), CuZn2ASxSe4-x consisting primarily of earth-abundant elements for applications in photovoltaic devices. A modified hot-injection method was used to synthesize these semiconductor NCs containing both S and Se chalcogens. The novelty of the new semiconductor NCs lies in the incorporation of multiple cations as well as two different chalcogen anions within the crystal lattice, which is an achievement from the materials synthesis aspect. The composition-controlled optical and photoluminescence properties of the CuZn2ASxSe4-x NCs were investigated via multi-modal material characterization including x-ray diffraction (XRD), ultraviolet-visible (UV-vis) spectroscopy, and photoluminescence spectroscopy (PL). The crystal structure, as determined from the XRD primarily consisted of the metastable wurtzite (P63mc) phase. The NCs exhibited direct band gap in the visible range that could be tuned both by varying the group III cation within the composition as well as the ratio of S/Se, based on the Tauc plot obtained from the UV-vis characterization. This work lays the groundwork for future investigations into the practical applications of copper chalcogenide NCs in solar energy conversion.

Committee: Soubantika Palchoudhury (Committee Chair); Guru Subramanyam (Committee Member); Robert Wilkens (Committee Member); Robert Wilkens (Committee Member); Guru Subramanyam (Committee Member); Kevin Myers (Advisor); Soubantika Palchoudhury (Committee Chair) Subjects: Aerospace Materials; Alternative Energy; Analytical Chemistry; Biochemistry; Chemical Engineering; Chemistry; Energy; Engineering; Environmental Science; Industrial Engineering; Information Science; Inorganic Chemistry; Materials Science; Nanoscience; Nanotechnology; Nuclear Chemistry; Nuclear Engineering

Doctor of Philosophy (Ph.D.), University of Dayton, 2023, Electrical Engineering

In this dissertation, electromagnetic (EM) propagation in a chiral material with dispersion up to the first order is examined for possible emergence of negative refractive index under non-conductive losses. Three loss scenarios are considered, viz., dielectric losses (complex permittivity); magnetic losses (complex permeability); and a combination of both types of losses. A spectral approach combined with a slowly time-varying phasor analysis is applied, leading to the analytic derivation of EM phase and group velocities and corresponding indices. The velocities and indices are examined by selecting arbitrary dispersion parameters based on published practical values. The results indicate the emergence of negative index within specific RF modulation bands. The results presented are aimed at observing the polarization states of the fields under loss conditions. In addition to that, a method is suggested whereby the effects of dielectric and magnetic losses may be combined via appropriate Taylor coefficients such that the effective attenuation constant may be driven to zero via induced gain mechanisms arising from the dielectric and magnetic loss models. The second primary topic investigated in this work highlights the properties relative to thick lenses in the presence of chirality and material dispersion. A salient feature of a chiral thick lens is the inherent bimodal propagation via circular polarizations. Three different scenarios are considered, viz., first-order frequency-dependent material dispersion of the dielectric permittivity; the lens material being chiral; finally, the case of an airgap (shaped like a thick lens) 4 embedded in a chiral host. Under chirality, two sets of ABCD matrices are derived for right- and left-circularly polarized (RCP/LCP) modes. The analyses and results are compared with the standard achiral problem. For imaging purposes, a simple 1-D colored transparency is placed as an object before the thick lens in each scenario, with the tr (open full item for complete abstract)

Committee: Monish Chatterjee (Committee Chair) Subjects: Electrical Engineering

Doctor of Philosophy, University of Toledo, 2022, Physics

This dissertation represents a collection of related studies that employ the various capabilities of spectroscopic ellipsometry (SE) to characterize and gain insights into the properties of the materials of relevance to advanced cadmium telluride (CdTe) photovoltaic technology. The structural, optical, and electrical properties of the component layers of the CdTe solar cell have been investigated using different SE data collection modes and analysis techniques. The component layers of the CdTe solar cell are deposited on soda lime and TEC-15 glass substrates in the superstrate configuration, i.e., with the solar irradiance entering through the glass substrate. The key layers include a transparent conducting oxide front contact, typically pyrolytic fluorine-doped tin oxide (SnO2:F); a high resistivity transparent layer (HRT) of either pyrolytic SnO2, sputtered MgxZn1 xO (MZO), or both; semiconductor layers of either n-type cadmium sulfide (CdS), cadmium selenide (CdSe), or both; p-type CdTe; a p+ back contact interlayer typically copper based; and a metallic conducting back contact layer, such as gold. In this research, SE-deduced component layer properties have been correlated with the CdTe device performance parameters. Applying various SE capabilities not only identifies the correlations between the material properties and solar cell performance but also enables optimization of the preparation conditions (e.g., substrate temperature) and resulting properties (e.g., thickness) of the CdTe device components. First, we have employed UV-VIS SE and ex-situ mapping SE results to correlate between the CdSe optical and structural properties with the CdTe solar cell performance. The effects of varying CdSe layer thickness on the CdTe solar cell performance have been studied, focusing on the TEC-15/HRT/CdSe/CdTe/Cu/Au cell structure. A set of four 6.5 cm x 6.5 cm TEC-15/HRT structures were coated with different nominal thicknesses of CdSe for incorporation within the (open full item for complete abstract)

Committee: Robert Collins Dr. (Advisor); Jone Bjorkman Dr. (Committee Member); Stephen O'Leary Dr. (Committee Member); Randall Ellingson Dr. (Committee Member); Nikolas Podraza Dr. (Committee Member) Subjects: Meteorology; Optics; Physics

Master of Science in Materials Science and Engineering (MSMSE), Wright State University, 2021, Materials Science and Engineering

Methylammonium lead triiodide (MAPbI3) has garnered attention due to their high solar cell efficiencies and low cost to manufacture, but commercialization is not yet possible owing to poor environmental stability. Thus, researchers seek ways which optimize the performance of the MAPbI3 solar cell by modifying the architecture and through interfacial engineering of the charge transport layers. Difficulties in understanding these devices arise from ion migration, charge separation and recombination, and metastable, thermally active precessions of the methylammonium (MA) moiety in the lead iodide framework. In this work, focus is given to the perovskite and an adsorbed monolayer, 2,3,4,5,6-pentafluorothiophenol (C6F5SH), which has demonstrated to increase environmental stability and solar cell efficiency when placed at the perovskite/hole transport layer interface. Utilizing a first principles approach, the interface of MAPbI3 and C6F5SH is explored using various metastable methylammonium orientations to understand the relative stability, electronic properties, bandgap, and infer impact on solar cell performance.

Committee: Amir A. Farajian Ph.D. (Advisor); Hong Huang Ph.D. (Committee Member); Raghavan Srinivasan Ph.D., P.E. (Committee Member) Subjects: Materials Science

Master of Science in Chemistry, Youngstown State University, 2021, Department of Biological Sciences and Chemistry

The semiconductor cadmium telluride (CdTe) has become the leading material for thin-film photovoltaic applications. Among the many techniques for preparing these thin films, electroless deposition, commonly known as chemical bath deposition, deserves special focus since it has been shown to be a pollution-free, low-temperature and inexpensive method. In this project, CdTe thin films were deposited on stainless steel 304 by the electroless deposition method using cadmium acetate and tellurium oxide dissolved in pH 12.5 NH3(aq). The deposition was based on the gradual release of cadmium ions (Cd2+) and the gradual addition of tellurium as TeO3 2- and their subsequent reduction in a hot aqueous alkaline chemical bath at 70 °C. This was attained by adding a complexing agent such as ammonia and a chemical reducing agent. Using triethanolamine as a complexing agent produced similar results. The following reducing agents were used: aluminum, sodium hypophosphite, formaldehyde, sodium borohydride and hydrazine. All of them deposited a film on stainless steel containing Cd and Te, but formaldehyde produced the best films in terms of uniform thickness, photosensitivity, and rapid growth rate. Electroless deposition of a thin Pt layer on top of the CdTe film improved the cathodic CdTe polarization for hydrogen evolution. The structural and morphological properties of the resulting films were characterized using X-ray diffraction (XRD), stylus profilometry, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) while the light/dark voltametric methods were used to determine the films' photosensitivity.

Committee: Clovis Linkous PhD (Advisor); Timothy Wagner PhD (Committee Member); Christopher Arnsten PhD (Committee Member) Subjects: Chemistry; Energy; Experiments; Materials Science

Master of Science in Mechanical Engineering, Cleveland State University, 2020, Washkewicz College of Engineering

Solar power has been identified as key technology required for extensive exploration of the moon and space. However, solar cell design so far has been based on earth and earth orbit environments, which is vastly different from the lunar surface. The Photovoltaic Investigation on the Lunar Surface (PILS) is a small payload carrying a set of solar cells of the latest technology to the moon in order to test the cells' feasibility and viability in the lunar environment. The objective of this thesis is to analyze the PILS payload design in its mission environments and optimize the thermal design to ensure that the critical components remain within their survival limits throughout transit and within operational temperature limits during lunar surface operations. The thermal analysis software Thermal Desktop was used to create a thermal model of the PILS payload which was analyzed in transit, three lunar orbits, descent and lunar surface operations in order to optimize the payload's active and thermal design. This thesis discusses the thermal model in detail which includes the geometry, conduction through the assembly, environmental conditions, and orbital definitions. The thermal model was then analyzed to investigate the temperature change in each component in all environments with the critical electronic components. The active thermal protection, heaters, were optimized for a “0 sink” case where the PILS payload was assumed to be in deep space – with no view to the sun or the moon for solar, albedo or planetshine heating. The passive thermal protection design was optimized for the hottest scenario in this mission: lunar noon during surface operations on the moon. Finally, the effects on the PILS payload from landing off-nominally on the lunar surface was also analyzed. The results show that the overall thermal design is successful in keeping all critical components within their operational temperature range throughout the entire mission.

Committee: Maryam Younessi Sinaki PhD. (Advisor); Tushar Borkar PhD. (Committee Member); Brian Motil PhD. (Committee Member) Subjects: Mechanical Engineering