Berlin 2015 – scientific programme
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O: Fachverband Oberflächenphysik
O 8: Organic-Inorganic Perovskite Semiconductors (HL with CPP)
O 8.4: Talk
Monday, March 16, 2015, 10:15–10:30, ER 164
Rutherford Backscattering Spectroscopy of Mass Transport by Transformation of PbI2 into CH3NH3PbI3 within np-TiO2 — •Felix Lang1, Albert Juma1,2, Voranuch Somsongkul1,3, Thomas Dittrich1, and Marisa Arunchaiya3 — 1Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany — 2Tallinn University of Technology, Department of Materials Science, Ehitajate tee 5, Tallinn 19086, Estonia — 3Department of Materials Science, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand
A key technique in methylammonium lead iodide (CH3NH3PbI3) thin film preparation is the sequential transformation of an inorganic precursor layer such as PbI2, infiltrated in nanoporous TiO2 to the final CH3NH3PbI3 by dipping into an organic precursor solution containing CH3NH3I. Here, we present an investigation on the mass transport during transformation by Rutherford backscattering spectroscopy (RBS). Energy dispersive X-Ray (EDX) spectroscopy mapping of cross sections first, revealed a homogenious PbI2 infiltration in nanoporous TiO2 before transformation and second, an accumulation of Pb and I at the surface after transformation. Quantitative depth profiles of Pb and I were obtained from RBS analysis. An instant degradation of CH3NH3PbI3 upon 4He+ ion radiation was found. The concentration profiles of Pb could be simulated with a one dimensional diffusion model taking into account an effective diffusion coefficient of Pb in the nanocomposite (about 1.5·10−11 cm2/s) as well as a parameter considering frazzling at the surface due to formation of crystallites.