Valence band dispersion measured in the surface normal direction of CH3NH3PbI3 single crystals

The electronic structure of methylammonium lead iodide (CH3NH3PbI3) single crystal surface has been studied by angle-resolved photoemission spectroscopy with synchrotron radiation. From energy dependence of normal emission spectra, we observe a top valence band dispersion of about 0.2 eV, which is originated from hybridized states of Pb-6s and I-5p. The inner potential of CH3NH3PbI3 is estimated to be -3 eV. Moreover, obtained lattice constants along the surface normal direction is 6.25 angstrom, which agree well to the lattice constant of a cubic phase in CH3NH3PbI3, confirm the structure of surface layers at 300 K is predominated by a cubic phase. (C) 2019 The Japan Society of Applied Physics