The conduction band dispersion in methylammonium lead iodide (CH3NH3PbI3) was studied by both angle-resolved two-photon photoelectron spectroscopy (AR-2PPE) with low photon intensity (similar to 0.0125 nJ/pulse) and angle-resolved low-energy inverse photoelectron spectroscopy (AR-LEIPS). Clear energy dispersion of the conduction band along the Gamma-M direction was first observed by these independent methods under different temperatures, and the dispersion was found to be consistent with band calculation under the cubic phase. The effective mass of the electrons at the Gamma point was estimated to be (0.20 +/- 0.05)m(0) at the temperature of 90 K. The observed conduction band energy was different between the AR-LEIPS and AR-2PPE, which was ascribed to the electronic-correlation-dependent difference of initial and final states probing processes. The present results also indicate that the surface structure in CH3NH3PbI3 provides the cubic-dominated electronic property even at lower temperatures.
Funding Agencies|JSPS KAKENHIMinistry of Education, Culture, Sports, Science and Technology, Japan (MEXT)Japan Society for the Promotion of ScienceGrants-in-Aid for Scientific Research (KAKENHI) [JP26248062, JP18H03904, JP26288007]; Futaba Research Grant Program of the Futaba Foundation; Qing-Lan Project from Yangzhou University; China Scholarship CouncilChina Scholarship Council