Electronic Structure of MAPbBr3 Single Crystals Probed by Photoluminescence and Surface Potentials
Hye Ri Jung a, Bich Phuong Nguyen a, Trang Thi Thu Nguyen a, Seokhyun Yoon a, William Jo a
a Ewha Womans University, 52, Ewhayeodae-gil, Seodaemun-gu, Seoul, 120, Korea, Republic of
nanoGe Perovskite Conferences
Proceedings of Perovskite Thin Film Photovoltaics (ABXPV17)
València, Spain, 2017 March 1st - 2nd
Organizers: Henk Bolink and David Cahen
Poster, 043
Publication date: 18th December 2016

CH3NH3Pb(Br,I)3 single crystals are interesting for understanding fundamental properties and potential applications for large-area crystalline substrates.  Most studies of all, examination on high photo-conversion efficiency thin-films are proceeded to comprehend the conducting characteristics. Grain growth behavior in perovksite is not fully controlled in terms of compositions, textures, and even believed as a trapping source of ionic migration. Surface potential of perovskites is known to depend strongly on the grain boundaries [1,2]. Singe crystals with no grain boundaries are, therefore, a material form for studying intrinsic properties. We investigated perovskite thin-films grown on TiO2 mesoscopic or planar bottom electrodes. We measured temperature dependent photoluminescence and Raman scattering spectroscopy in order to investigate bandgaps and vibrational characteristics. The distribution of surface electric potential and current transport was studied by Kelvin probe force microscopy and conductive atomic force microscopy respectively. Surface potentials of iodide and bromide films exhibit distribution around 4.4 eV and 4.6 eV, respectively. Current level of the mono-grain is small but some spots exhibit large current values at high external voltage bias. Consolidated information of the band gap and workfunction will provide a schematic picture on the electronic structure of the perovskite materials. 

[1] G. Y. Kim, S. H. Oh, B. P. Nguyen, W. Jo, B. J. Kim, D. G. Lee, H. S. Jung, “Efficient Carrier Separation and Intriguing Switching of Bound Charges in Inorganic−Organic Lead Halide Solar Cells”, Journal of Physical Chemistry Letters, 6, 2355 (2015).[2] Daehan Kim, Gee Yeong Kim, Changhyun Ko, Seong Ryul Pae, Yun Seog Lee, Oki Gunawan, D. Frank Ogletree, W. Jo, and Byungha Shin, “The effect of post-synthesis annealing duration on grain properties and photovoltaic performance of organic-inorganic hybrid perovskites”, Journal of Physical Chemistry-C, 120, 21330 (2016).



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