Fabrication of Lead-Free MASn(I,Br)3 Solar Cells and Their Stability Probed by Scanning Probe Microscopy
William Jo a, Bich Phuong Nguyen a
a Ewha Womans University, 52, Ewhayeodae-gil, Seodaemun-gu, Seoul, 120, Korea, Republic of
Proceedings of Perovskite Thin Film Photovoltaics (ABXPV17)
València, Spain, 2017 March 1st - 2nd
Organizers: Henk Bolink and David Cahen
Oral, presentation 046
Publication date: 18th December 2016

Methylammonium lead halide perovskites have been considered to be promising photovoltaic materials due to their large absorption coefficient, high carrier mobility, high carrier diffusion length, and direct band gap. We investigated the electrical properties of lead-free CH3NH3Sn(I,Br)3 perovskite materials under ambient conditions. The highest photo-conversion efficiency of the solar cells was 2.1% with TiO2 mesoporous structure. The work function and the local current were measured by Kelvin probe force microscopy and conductive atomic force microscopy. Surface potential distributions on grains and near grain boundaries of the Sn-based perovskite show a similar behaviors in the Pb-based perovskite [1,2]. The analysis of the physical quantities depending on time yields to us the extent of decomposition. An additional value of the surface potential shows up as the materials goes to degradation simultaneously with a sudden increase and subsequent relaxations of local current. The temporal behaviors of the surface potential and local current represent the instability of the perovskite material. Based on the understanding of the degradation mechanism, we will pave a way for improved photo-conversion efficiency in environment-friendly perovskite solar cells. 

[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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