First-principle Study Of MAPbBr₃

Hybrid organic-inorganic perovskite-like(HOP) materials were gradually developed in the past half century, and showed unique value in transistors, sensors, LED, solar cells, and other applications. In particular, the application of MAPbX3(MA is methylamine, whose chemical formula is CH3NH3; X=Cl, Br, I) in solar cells was developed rapidly, and a top power conversion efficiency of 21% has been achieved. A large number of calculations applying first principle calculation methods has been conducted to study its electronic structures, exciton properties, and defect physics for characteristics understanding or modulation, and got many important results. But theoretical works on MAPbBr3 were still incomplete, especially for the newly developed HOP quantum wires or quantum dots, which need to be studied in detail.In this thesis, we use VASP to conduct the first principle study on the electronic structure and defect physics of MAPbBr3.(1)After structure optimization and electronic structure calculation, we analyzed its basic electronic property, and found it a direct-bandgap semiconductor with small electron/hole effective mass.(2)We analyzed the thermaldynamic equilibrium conditions for material stability, and calculated all the 12 types of defects in MAPbBr3 for its 4 crystal phases. We found that MAPbBr3 shows excellent self-doping p-type conductivity and can hardly be modified to n-type by altering the synthesis condition or doping foreign atoms. After calculation and analyses, it’s advised to adopt Br-rich/Pb-poor condition to grow defect-free and structure-perfect MAPb Br3 materials.(3)The synthetized MAPbBr3 quantum dots has a photoluminescent quantum yield of 70% in our library. We built the cube model of quantum dots by combining the energy dispersive spectrum measurements. These works help to understand and modulate the characteristics of MAPbBr3, and give advices on experimental works.