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Improvement of the stability of perovskite solar cells in terms of humidity/heat via compositional engineering

Compositional engineering is one of the ways of controlling the phase structure and improving the stability of perovskite solar cells. This study is the investigation of how adding cesium (Cs) to formamidium lead iodide (FAPbI3) perovskite affects the structure, morphology, performance and stability of hole-transport-free (HTF) mesoporous solar cells. It was shown that this addition leads to decrease in the lattice constant and the tolerance factor and causes perovskite band gaps to vary. The x-ray diffraction analysis also showed the removal of the non-photovoltaic perovskite phase and the conversion of the trigonal black phase to tetragonal structure. As 15% of Cs was added, the average efficiency of 7.41% and the highest efficiency of 11.78% were achieved for the HTF solar cells. Finally, FA0.85 Cs0.15PbI3 perovskite cells proved to be more stable than FAPbI3 reference cells at 150 °C and the humidity of 90%.