Recently, solid-state solar cells using organic-inorganic metal halide as a sensitizer have attracted a lot of interest and showed a promising progress as an alternative for conventional dye sensitized solar cells. Organic-inorganic metal halides, which are based on lead iodide have several properties that make them an interesting material to be used as light harvesting and charge-transporting components in solar cells, e.g direct band gap, large absorption coefficient and high carrier mobility. Although finding a solution processed compound that can provide quality device characteristics and shows reasonably decent function in combination with other components in solar cells, represents a challenge in this field.  Recently perovskite thin film solar cells based on methyl ammonium lead iodide as light absorber in combination with spiro-OMeTAD as hole transport material showed a remarkable performance up to 16.2% conversion efficiency. In the present work, we investigated the effect of crystal structure on the electronic properties of the perovskites by varying the alkyl-ammonium cation. It is proposed, that the organic cation in this structure does not have a major role in the electronic band structure, is used to maintain the neutrality of the crystal lattice, while the major role is dependent on the lead halide anion. However the size of cation is very important in the 3D structural of the material. As shown from the crystal structure of the materials, the cation is embedded in the gap between the lead iodide structural units which are sharing octahedral corners. Different size of cations has effect on the distance of lead iodide structural units, and it significantly changes the structure of the compounds. We have focused on the effect of this change in order to obtain fundamental information about the compound and connect it to the performance of the solar cells based on these compounds. We fabricated three different alkyl ammonium iodide salts and used them to prepare alkyl-ammonium lead iodide compound. Compounds are methyl-ammonium lead iodide, ethyl-ammonium lead iodide and propyl-ammonium lead iodide.Characterizations of the compounds were done by powder and single crystal X-ray diffraction. Uv-visible spectra of the samples were collected in order to investigate structural and spectral relation in these compounds. Compounds were used in solar cells to examine performance of the solar cells by changing the cations in the alkyl ammonium lead iodide compounds.

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