1 Light-Induced Increase of Electron Diffusion Length in a p-n Junction Type CH 3 NH 3 PbBr 3 Perovskite Solar Cell Nir Kedem 1, *, Thomas M. Brenner 1, *, Michael Kulbak 1 , Norbert Schaefer 2 , Sergiu Levcenko 2 , Igal Levine 1 , Daniel Abou-Ras 2 , Gary Hodes 1 , David Ca- hen 1 *equal contribution 1. Dept. of Materials & Interfaces, Weizmann Inst. of Science, Rehovot, Is- rael 76100 2. Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn- Meitner-Platz 1, 14109 Berlin, Germany ABSTRACT: High band-gap, high open-circuit voltage solar cells with methylammonium lead tri-bromide (MAPbBr 3 ) perovskite absorbers are of interest for spectral splitting and photo-electrochemical applications, because of their good per- formance and ease of processing. The physical origin of high performance in these and similar perovskite - based devices remains only partially under- stood. Using cross-section electron-beam-induced current (EBIC) measure- ments, we find an increase in carrier diffusion length in MAPbBr 3 (Cl)-based solar cells upon low intensity (~few % of 1 sun intensity) blue laser illumi- nation. Comparing dark and illuminated conditions, the minority carrier (electron) diffusion length increases about 3.5 times from L n = 100 ± 50 nm to 360 ± 22 nm. The EBIC cross-section profile indicates a p-n structure be- tween the n-FTO/TiO 2 and p-perovskite, rather than the p-i-n structure, re- ported for the iodide derivative. Based on the variation in space-charge re- gion width with varying bias, measured by EBIC and capacitance-voltage measurements, we estimate the net-doping concentration in MAPbBr 3 (Cl) to be 3-6x10 17 cm -3 . brought to you by CORE View metadata, citation and similar papers at core.ac.uk provided by HZB Repository