An LED-based solar simulator has been designed, constructed, and qualified under ASTM standards for use in the Cal Poly Space Environments Laboratory. The availability of this simulator will enhance the capability of undergraduate students to evaluate solar cell and thermal coating performance, and offers further research opportunities. The requirements of ASTM E927-19 for solar simulators intended for photovoltaic cell testing were used primarily, supplemented by information from ASTM E491-73 for solar simulators intended for spacecraft thermal vacuum testing. Three main criteria were identified as design goals - spectral match ratio, spatial non-uniformity, and temporal instability. An electrical design for an LED-based simulator to satisfy these criteria was developed and implemented, making use of existing lab equipment where possible to minimize cost. The resulting simulator meets the desired spatial non-uniformity and temporal instability requirements of ASTM E927-19, but falls short of the spectral match ratio needed. This is shown to be due to a calibration issue that is easily amended via software. The simulator is overall Class UCB under ASTM E927, and Class CCC under ASTM E491. The simulator was used to conduct the same laboratory procedure for solar cell I-V curve testing as performed by undergraduate students, showing excellent promise as a course enhancement.

Research to increase the efficiency of conventional solar cells is constantly underway. The goal of this work is to increase the efficiency of conventional solar cells by incorporating quantum dot (QD) nanoparticles in the absorption mechanism. The strategy is to have the QDs absorb UV and fluoresce photons in the visible region that are more readily absorbed by the cells. The outcome is that the cells have more visible photons to absorb and have increased power output. The QDs, having a CdSe core and a ZnS shell, were applied to the solar cells as follows. First, the QDs were synthesized in an octadecene solution, then they were removed from the solution and finally they were dried and deposited into polydimethylsiloxane (PDMS) and the PDMS/QD composite is allowed to cure. The cured sample is applied to a silicon solar panel. The panel with the PDMS/QD application outputs 2.5% more power than the one without, under identical illumination by a tungsten halogen lamp, using QDs that fluoresce in the orange region. This work demonstrates the feasibility of incorporating QDs to increase the efficiency of conventional solar cells. Because the solar cells absorb better in the red region, future effort will be to use QDs that fluoresce in that region to further boost cell output.

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Renewable and clean energy is urgently needed to cope with the climate crisis. Photovoltaics (PV) has been the fastest growing technology in the clean energy market due to its low cost, and the abundance of solar energy. The capacity of silicon-based PV is rapidly expanding with evolving technologies. Passivating the solar cell’s electrical contacts is a widely accepted strategy for the PV industry to improve device power conversion efficiency (PCE). Polycrystalline silicon (Poly-Si) passivating contacts are one of the promising concepts in the emerging class of passivating contacts. In this dissertation, the passivation mechanism of Poly-Si passivating contacts is investigated. Moreover, the influence of dopant diffusion on the passivation quality is revealed. To address the side-effects of dopant diffusion, a thin buffer layer is inserted between the Poly-Si(p) layer and the $SiO_x$ layer. With such a buffer layer, the passivation of the Poly-Si passivating contact is improved, which in turn, enhances the device PCE. In addition to passivating contacts, this dissertation also explores carrier-selective contact of crystalline silicon (c-Si) and low work function metal – Li. Li is a very reactive metal which makes the fabrication process a challenge. To overcome such a challenge, the c-Si/ Li contact is fabricated by thermally decomposing stable $Li_3N$ powder instead of metal evaporation. The c-Si/Li contact shows an excellent electron-selective transport performance with a 0.39 eV energy barrier. Full-area Si/Li rear contact devices are fabricated, and >19% PCE and >80% fill factor are achieved. To accelerate the device optimization, a physical model embedded machine-learning approach is applied to transparent conductive oxide (TCO) materials optimization. In this work, empirical correlations between sputtering parameters and the deposited TCOs’ electrical properties are established. Then a Bayesian Parameter Estimation (BPE) algorithm is applied to learn the empirical model. With this BPE network, the TCOs’ electrical properties are successfully predicted with limited material characterizations. Thanks to the combination of BPE and a physical model network, the material optimization process is significantly accelerated. In summary, this dissertation explores different aspects to develop novel passivating and carrier-selective contacts for c-Si solar cells, and introduces an approach to accelerate the development processes.

In thin film solar cells there is a front contact layer called TCO, transparent conducting oxide. This layer requires high conductivity and high transmittance. Different materials such as Tin doped indium oxide (ITO) and Aluminum doped zinc oxide (AZO) are current good alternatives but several other materials are investigated to find even better materials. One of them is tungsten doped indium oxide (IOW). This project was about investigating the deposition process for IOW and characterize the properties of IOW thin film to investigate the possibilities for implementing this material as a contact layer in thin film solar cells. The results from the two batches of depositions varied a lot. Some samples came out dark, but some were transparent and had a high transmittance, suitable for a TCO. The highest transmittance reached through this process was around 95 % in the infrared (IR) range and around 90 % in the visible range. When it comes to the resistivity, no IOW-samples reaches desired levels for a TCO. The lowest resistivity reached was 6.36 * 10-4 W cm. The results showed that the sample with the lowest resistivity was the undoped material, which is contradicting the current theory on the subject. The lowest resistivity for the IOW film was 6.50 * 10-3 W cm.

Syftet var primärt att undersöka hur stor degraderingen hos svenska solcellssystem, som varit i drift mellan 3 och 9 år, är. Data över produktion samlades in från 37 anläggningar i Mellansverige och normaliserades för meteorologiska förutsättningar. Det erhölls en årlig försämringstakt av normaliserad produktion på 1,4 % i medeltal. Resultatet ansågs inte vara tillräckligt väl normaliserat och kunde därför inte approximera degraderingstakten. Dessutom fanns för många osäkerheter, framför allt i strålnings- och temperaturdatan, för att resultatet skulle kunna bli trovärdigt. Globalstrålningsdata mätt för varje solcellsanläggning samt paneltemperatur istället för lufttemperatur hade behövts användas. Ett mer trovärdigt resultat skulle dessutom kunna erhållas genom att använda data från fler och äldre anläggningar, där yttre parametrar som exempelvis skuggning, utbyggnad av anläggning och byte av komponenter varit känt. En analys av en mer än 30 år gammal solcellsanläggning utfördes där den visade sig fortfarande producera ungefär lika mycket el som när den installerades. Anläggningen visade därmed på att solceller kan hålla en lång tid i svenska förhållanden. Slutligen undersöktes tillgängligheten av el från solcellssystem genom utskick av formulär till olika solcellsinnehavare. Det visade sig att ingen specifik komponent var överrepresenterad när problem uppstod samt att större och äldre anläggningar i större utsträckning stötte på problem som påverkade deras elproduktion. Tillgängligheten visade sig vara god.

Humanity has great energy demands, and must simultaneously combat climate change by curbing anthropogenic greenhouse gas emissions. Perovskite solar cells (PSC) provide a low-carbon energy source, at lower production costs than traditional silicon-based solar cells. PSC's suffer some issues with long-term stability. This report presents a measurement aimed at better understanding interfacial dynamics of PSC's, using X-ray Photo-electron Spectroscopy (XPS). By collecting data at the synchrotron BESSY II, material compositions at different depths in the cell were successfully measured. An unexplained shift in binding energy was observed for configurations with an external light source on and off.

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