[8a-A501-1~10] 12.5 Organic solar cells

[8a-A501-5] The Surface Electronic Structure of Hybrid Organo Lead Bromide Perovskite Single Crystals

〇Takashi Komesu¹, Xin Huang^1,2, Tula Paudel¹, Yaroslav Losovyj³, Xin Zhang¹, Eike Schwier⁴, Yohei Kojima⁵, Mingtian Zheng⁵, Hideaki Iwasawa⁴, Kenya Shimada⁴, Makhsud Saidaminov⁶, Dong Shi⁶, Ahmed Abdelhady⁶, Osman Bakr⁶, Evgeny Tsymbal¹, Peter Dowben¹ (1.Univ. Nebraska, 2.Southeast Univ., 3.Indiana Univ., 4.HiSOR, 5.Hiroshima Univ., 6.KAUST)

Keywords:Electronic band structure, Density functional theory, Angle-resolved photoemission and inverse photoemission spectroscopy

The electronic structure and band dispersion of methylammonium (MA = CH₃NH₃⁺) lead bromide, CH₃NH₃PbBr₃, has been investigated through a combination of angle-resolved photoemission spectroscopy (ARPES), Fig. 1 and 2, and inverse photoemission spectroscopy (IPES), Fig. 2, as well as theoretical modeling based on density functional theory (DFT). The experimental band structures are consistent with DFT calculations. The results demonstrate the presence of a dispersive valence band in MAPbBr₃ that peaks at the point of the surface Brillouin zone (SBZ), Fig. 1. The results also indicate that the surface termination of the MAPbBr₃ is the methylammonium bromide (MABr) layer, discussed in our presentation. We find our results support models that predict a heavier hole effective mass in the region of -0.23 to -0.26 m_e, along the (SBZ center) to point of the SBZ edge. The surface appears to be n-type as a result of an excess of lead in the surface region.