The stability and electrical properties of alkali metal cations doped CH3NH3PbI3

Inhalt:
The band structure and density of states of (CH3NH3)0.75A0.25PbI3 (A=Li (exp+), Na(exp +), K(exp +)) is calculated using the ultrasoft pseudopotentials (USPs). As results shown, the tolerance factor t of the three systems close to 1, it reflects that the doped structures are stable, dopant formation energy of CH3NH3PbI3 doped with K(exp+) is -0.893 eV, which indicate that this structure is most stable. Energy band structures of the three systems doped are similar, the band gap in the range of 1.6~1.9 eV is suitable for solar cells device. With the increase of alkali metal cation radius, the band gap of corresponding structure decreases, where K(exp+) has the greatest effect on the regulation of band gap. The top of the valence band is composed of I 5p orbitals, while the bottom of the conduction band consists of Pb 6p orbitals. The divergence in stability and electrical properties are mainly due to the different CH3NH3PbI3 structures. These results can provide theoretical guidance for further in-depth research and experiments of perovskite solar cells.