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Stability Study of Organic-inorganic Hybrid Perovskite Solar Cells
Organic-inorganic hybrid perovskites (OIHPs) have attracted increasing attention because of their extraordinary properties, such as large absorption coefficient, long carrier diffusion length, solution processability, low temperature compatibility, low cost, and scalability. OIHPs have huge potential applications in solar cells, photodetectors, radiation detectors, and x-ray imaging. OIHP solar cells have been considered as one of the most promising candidates for harvesting solar energy. But the stability of OIHP solar cells needs to be enhanced. In this dissertation, stability issues of perovskite solar cells are mainly discussed. In Chapter 1, OIHPs are introduced, including their crystal structures, compositions, and optoelectronic properties. The background of this OIHP solar cell stability is comprehensively reviewed. In Chapter 2, the perovskite fabrication procedures and characterization methods are described. In Chapter 3 and Chapter 4, the stability of perovskite solar cells is studied from both external and inner factors. In Chapter 3, the copper electrode is evaluated to be a stable electrode for perovskite solar cells. In encapsulated devices, perovskite in direct contact with copper showed no reaction at laboratory time scales and is predicted to be stable over 22 years at the nominal operating cell temperature of 40 °C. After long-term thermal annealing and illumination, no copper diffusion and copper-induced trap states were observed. In Chapter 4, residual strain in polycrystalline perovskite films is first unveiled. In the out-of-plane direction, the polycrystalline films have compressive strain. Along the in-plane direction, it is tensile strain. The strain is caused by the large thermal expansion mismatch between the perovskite polycrystalline film and the substrate. Strain accelerates degradation of perovskite films under illumination due to the reduced activation energy of ion migration in the strained perovskite films. This research work paves the way for enhancing the stability of perovskite solar cells.
Zhao, Jingjing, "Stability Study of Organic-inorganic Hybrid Perovskite Solar Cells" (2019). ETD collection for University of Nebraska - Lincoln. AAI13860747.