Optical, Structural and Morphological Characterization of Germanium Doped Cesium Tin Triiodide for Perovskite Solar Cells Applications

Marion Mogusu^1, , Duke Oeba¹ and Cliff Mosiori²

¹Department of Physics, Faculty of Science, Egerton University, P.O. Box 536-20115, Egerton, Kenya

²Department of Mathematics and Physics, Technical University of Mombasa, P.O. Box 90420-80100, Mombasa, Kenya

Cite this paper:
Marion Mogusu, Duke Oeba and Cliff Mosiori. Optical, Structural and Morphological Characterization of Germanium Doped Cesium Tin Triiodide for Perovskite Solar Cells Applications. International Journal of Physics. 2025; 13(3):62-68. doi: 10.12691/ijp-13-3-3

Abstract

In this work, germanium doped cesium tin triiodide (CsSnI₃-Ge) perovskite thin films, incorporated with a 5mole% germanium (Ge) concentration were deposited on fluorine doped tin (IV) oxide (FTO) substrates using spin coating technique and the films were synthesized under different spin coating speeds. Ge was used as a dopant to curb the problem of the rapid oxidation of tin (II) ions (Sn²⁺) to tin (IV) ions (Sn⁴⁺) in the presence of oxygen. Optical measurements were done using ultraviolet visible (UV-Vis) spectrophotometer, structural measurements were carried out using an X-ray diffraction (XRD) machine and the morphological analysis was done using a scanning electron microscope (SEM). The CsSnI₃-Ge layer deposited at a spin coating speed of 4000 revolutions per minute(rpm) displayed the highest absorbance with a band gap value in the range of 2.85 eV to 3.36 eV which was higher than the ideal value of ~1.5 eV. Structural analysis on the different CsSnI₃-Ge films displayed a consistent orthorhombic structure across all samples and SEM images revealed almost identical crystallite sizes. Generally, the perovskite film synthesized by spin coating speed of 4000 rpm displayed higher absorbance, higher crystallinity and a possibly uniform film morphology making it the optimal layer for solar cell applications.

Keywords:
Perovskites tin oxidation spin coating thin films

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