Interfacial Metal Oxides for Hybrid Solar Cells

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ZIMMERMANN, Eugen, 2019. Interfacial Metal Oxides for Hybrid Solar Cells [Dissertation]. Konstanz: University of Konstanz

@phdthesis{Zimmermann2019Inter-53909, title={Interfacial Metal Oxides for Hybrid Solar Cells}, year={2019}, author={Zimmermann, Eugen}, address={Konstanz}, school={Universität Konstanz} }

2021-06-08T11:33:43Z terms-of-use 2021-06-08T11:33:43Z Zimmermann, Eugen eng 2019 Emerging photovoltaics describe the latest class of solar cells designed to satisfy mankind’s need for more clean electricity. Therefore, new low-cost materials are used in multi-layer stacks, which are often also produced by cost-effective processes. Due to the great effort of the research community, the efficiency of solar cells has increased considerably over the past decades and, with perovskite solar cells, now approaches the level of conventional silicon cells. For commercialization, however, the characterization of power conversion efficiency and other device characteristics must be reliable. While, many challenges and measurement requirements have been identified in the past many of them have yet to find universal adaptation throughout the research community. Thus, no or incorrect shadow masks are used during measurement or the so-called „hysteretic behaviour“ of perovskite solar cells is neglectfully ignored, which results in greatly overestimated efficiencies or biased conclusions. Therefore, the challenges, requirements and recommendations for a correct determination of efficiency are explained and an improved measurement protocol is proposed in order to raise awareness of, and help avoid, the most common sources of error. For further efficiency improvement, the remaining limitations of fabricated devices must be identified and overcome, which requires appropriate tools for controlled investigations. One such tool is spatial atomic layer deposition, which extends the advantages of conventional ALD by a vacuum-free deposition and an largely increased deposition speed. The precise control of deposition parameters allows a detailed investigation of layer properties and their influence on device characteristics. Based on this, important questions regarding interaction of morphology and crystallinity, conductivity and energy band alignment, as well as their implications for charge transport and recombination processes may be answered. Therefore, deposited TiO<sub>2</sub> layers are investigated by different structural and optoelectronic characterization techniques and successfully applied as electron transport layers in Sb<sub>2</sub>S<sub>3</sub>- and perovskite-based solar cells. The analysis of layer structure and optical properties reveal a transition from amorphous layer growth at low temperatures to highly crystalline anatase films, which is accompanied by an simultaneous increase in layer density, surface roughness, refractive index, and a reduced optical bandgap. Integrated in solar cells, however, the influence of these layer properties is largely superimposed by the influence of the interface, which, particularly in perovskite solar cells, requires passivation in order to improve charge extraction and to reduce surface assisted recombination. This may be achieved by core-shell structures for which a possible fabrication approach is demonstrated by the stepwise and gradual deposition of continuous TiO<sub>2</sub> layers of different temperatures. Interfacial Metal Oxides for Hybrid Solar Cells Zimmermann, Eugen

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