Odhiambo, Cephas Rohn2026-01-222026-01-222025http://41.89.96.81:4000/handle/123456789/3390Clean and renewable energy sources have experienced significant demand in recent years due to their necessity for sustainable industrial development. This requirement is also emphasized by the United Nations‘ Sustainable Development Goal 7, "Affordable and Clean Energy." The advent of perovskite solar cells has generated considerable interest in the energy sector, offering hope for advancements in solar technology. Perovskite solar cells are known for their high efficiency and ability to convert a wide range of light wavelengths into electricity. Additionally, these solar cells exhibit excellent charge carrier mobility, light absorption and have a high tolerance for structural defects. However, perovskite solar cells face challenges related to toxicity and instability. This research addressed these issues by investigating lead free FASnl2Br. Furthermore, incorporating bromine into FASnl3 and sulphur into ZnO was aimed at enhancing the stability solar cells fabricated with these materials. This approach improved thermal stability, resulting in a well-ordered, compact crystal lattice and reducing the propensity for phase transitions or degradation at higher temperatures. It also enhanced moisture stability through defect passivation. In this study, FASnIgBr and ZnO:S suitable for perovskite device applications was synthesized by spin coating using solution-based technique. Structural and optoelectronic characterization was performed using X-ray diffraction (XRD) and ultraviolet-visible (UV-Vis) spectroscopy, respectively. The ZnO:S was observed to show Wurtzite hexagonal structure that agrees with theoretical information. Finally, perovskite solar cells were fabricated on indium-doped tin oxide glass substrates using a spin coater. Doping enhanced the transmission through ZnO:S making it best suited as an electron transport layer (ETL) material. For FASnI;Br, the XRD structure exhibited peaks of a perovskite material. The doping increased optical absorption of FASnl3 making it best suited for perovskite material. A power conversion efficiency (PCE) of 16.5%, Jsc of21.3 mAcm'2 and Voc of 1.15 V were obtained using ZnO:S ETL tested with FAPbI3. The solar cell fabricated with FASnIgBr exhibited moderate performance and favourable electrical properties; PCE of 3.57%, Voc of 0.569 V and J sc of 0.568 mAcm'Z. It was also concluded that ZnO: 4%S performed better than ZnO: 8%S doping concentrations. This research significantly contributes to the field by developing non-toxic, stable materials for perovskite solar cells. The enhanced performance can still be achieved by studying interfacial layer materials as well as passivation materials. This will in future, revolutionize photovoltaic technology, paving the way for more efficient and durable solar energy solutions.enSolar cellsThesis