| Abstract [eng] |
Solar cells may provide our future with clean, cheap, and infinite energy. Nowadays, the most used solar cells are heavy, bulky, and manufactured pure silicon material requires a lot of expenses. However, different solar cells are being researched and studied more such as perovskite solar cells. Perovskite solar cells were discovered only a decade ago and they have already exceeded the efficiency of older generation solar cells. They are lightweight, durable, flexible and they do not require high fabrication costs. Nevertheless, they still cannot be used industrially due to their low moisture stability. Three-dimensional perovskite solar cells are typical perovskite solar cells that have high power conversion efficiency, yet are sensitive to humid environment and degrade fast. Two-dimensional perovskite solar cells, on the other hand, have quite low power conversion efficiency but their structure lets them incorporate organic spacer cations that could provide various properties. Integrating certain organic cations in two-dimensional perovskite and mixing them with three-dimensional perovskite could lead to the compositions with tunable properties and synergistic effect. Two-dimensional Ruddlesden-Popper phase consists of organic monoammonium cations, and it was the first to be studied, while Dion-Jacobson phase consists of organic diammonium cations which is relatively poor studied. Dion-Jacobson organic cations have an advantage over Ruddlesden-Popper cations – strongly covalently bonded perovskite fragments. Moreover, by having fluorine atoms in the cation structure, it is expected to enhance the moisture stability of perovskite compositions as these atoms are known to have water repellent properties. First of all, isomeric organic o, m, p-phenylenediethanamonium iodide cations for Dion-Jacobson phase were synthesised and only p-isomer was successfully integrated in two-dimensional perovskite structure to show a power conversion efficiency of 13.54 %, while o- and m-cations were not able to form Dion-Jacobson phase most probably due to the steric hindrance. Furthermore, synthesised isomeric cations having free ammonium groups were used as passivating agents on three-dimensional perovskite and solar cell having o-cation as an extra passivation layer showed the power conversion efficiency of over 23 % with increased moisture stability after 1000 hours in humid environment. Lastly, (perfluoro-1,4-phenylene)dimethanamonium and (perfluoro-1,4-phenylene)diethanamonium iodide cations were synthesised in order to increase the hydrophobicity of such systems. Further synthesis of divalent organic cations and their perovskite composition modification is essential in order to enhance the performance and stability of mixed perovskite-based solar cells. |
