Study on bandgap tuning of organometal halide perovskite

Shokri, Amirmasoud and Sattari, Farhad and Mirershadi, Mirershadi and Azizian-Kalandaragh, Yashar (2017) Study on bandgap tuning of organometal halide perovskite. Masters thesis, University of Mohaghegh Ardabili.

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Abstract

Solar cells made from hybrid perovskite semiconductors have seen an unprecedented rise in efficiency over the past few years, now reaching efficiency values close to the best silicon solar cells. However, the understanding as to why these materials perform so efficiently is lacking behind the device progress. According to the recent remarkable developments of lead halide perovskite solar cells, investigation of the optical and electronical properties of perovskite structures seems to be necessary. In this thesis, firstly Organic–inorganic CH3NH3PbX3 perovskite hybrids with X= Cl, Br and I are prepared by solution chemistry method. The effect of halogen atom on the electronical properties in this structure is studied experimentally. Our study concludes that the band gap energy can be tuned by varying the halogen atoms. Thus we believe that our studies will be beneficial for the fabrication of electronic and optical devises. Conventional semiconductors show either strong absorption and short charge carrier lifetime (direct bandgap semiconductors), or weak absorption and long lifetimes (indirect bandgap). Hybrid perovskites seem to offer both strong absorption and long lifetime, which is very convenient for solar cell operation. We show that the indirect bandgap appears at high pressure (1.2 GPa) in CH3NH3PbCl3 perovskite, and the bandgap increases with increasing pressure. We also show that the direct bandgap appears at high pressure (1.2 GPa) in CH3NH3PbBr3 perovskite, and the bandgap dicreases by increasing pressure. Inadition, CH3NH3PbI3 perovskite shows direct bandgap and the value of the bandgap decreases by incraeasing the pressure and reaches minmum at P=0.11GPa, and then is robust with further rise of pressure.

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