Browsing by Author "Kerubo, Mogusu Marion"

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    Fabrication and evaluation of germanium doped cesium tin triiodide perovskite solar cells
    (Egerton University, 2025) Kerubo, Mogusu Marion
    In the ever-evolving landscape of renewable energy technologies, perovskite solar cells (PSCs) have emerged as an alternative for efficient and affordable photovoltaics (PVs). The quest for sustainable energy sources, coupled with the need to eliminate toxic lead content has called for research in inorganic, cost effective and stable lead-free PSCs. In this work, tin (IV) oxide (S1102) electron transport layer (ETL) and gennanium doped cesium tin triiodide (CsSnI3-Ge) perovskite layer, incorporated with a 5mole% Ge concentration were deposited via thermal evaporation and spin coating methods respectively. In the deposition of SnO; films, the thickness was varied, and CsSnI3-Ge films were deposited under different spin coating speeds. Optical measurements were done using the ultraviolet visible (UV-Vis) spectrophotometer while structural and morphological measurements for the perovskite layers were performed using an X-ray diffraction (XRD) and scanning electron microscope (SEM) machines respectively. Our findings show that optical properties for the 30 nm thickness ETL displayed a higher transmittance of approximately 80%, and the band gap values ranged from 3.02 eV to 3.34 eV. The CsSnI3-Ge layer deposited at a spin coating speed of 4000 rpm displayed the highest absorbance of approximately 0.77 a.u attaining a band gap value in the range of 2.85 eV to 3.35 eV which was higher than the ideal value of ~l.5 eV. Structural analysis on CsSnI3-Ge films displayed a consistent orthorhombic structure across all samples. The crystallite sizes were nearly identical, as was seen in SEM images. Generally, the perovskite film synthesized by spin coating speed of 4000 revolutions per minute (rpm) displayed higher absorbance, higher crystallinity and a relatively uniform film morphology making it the optimal layer for fabrication. Three perovskite structures of fluorine doped tin (IV) oxide (FTO)/SnOz/CsSnI3-Ge/copper (I) oxide (Cu2O)/graphite were fabricated and their current density-voltage (J -V) characteristics investigated using a solar cell simulator. From the results, the best performing cell attained a power conversion efficiency (PCE) of 2.458% with an open circuit voltage (Voc) of 0.7056 V, a short circuit current density (J Sc) of 8.868 mA.cm‘ 2 and a fill factor (FF) of 39.27%. This output was less than expected but agrees with that of several Sn based PSCs. An optimal annealing temperature has been recommended for the SD02 ETL for band gap control as well as an all-vacuum environment for the synthesis of Sn based perovskites. Altemative synthesis routes for Ge doping should also be explored and interface/surface passivation strategies should be considered for an improved V09. Additionally, hall effect measurement is recommended to determine the charge carrier concentration. This study will help contribute to advancements in renewable energy technologies, research and promotion of sustainable energy solutions