Structural changes and band gap tunability with incorporation of n-butylammonium iodide in perovskite thin film.

The current work presents structural change and band gap tunability using hybrid organic-inorganic perovskite with the incorporation of long chain ammonium halide. Thin films of MAPbI with different ratio of n-butylammonium iodide (BAI) have been successfully deposited on the substrate using a single step coating technique. X-ray diffraction scans revealed the transition of the 3D structure of MAPbI to quasi-2D perovskite structure when BAI loading increase with a crystallite size range approximately 16 nm. This structural changeis reflected in the band gap as it increased from 1.59 eV for bulk crystal MAPbI to 2.13 eV for BAI and MAPbI ratio of 1:1. Correspondingly, photoluminescence measurement showed a blue shift in perovskite emission due to the transition of 3D to 2D layered structure perovskite. Raman spectra confirm that all fabricated films are of pristine quality and no corresponding degradation peaks of PbI is observed. These characteristics are important to address the single step deposition method of hybrid perovskite for perovskite solar cells application.