Presenter: Prof. Frank Schreiber,Institut für Angewandte Physik, Universität Tübingen, 72076 Tübingen, Germany
Topic: Perovskite-based solar cells: A closer look into the microscopic structure using X-rays
Time: 3:00 PM, Nov. 16th (Friday)
Location: Conference Room B, BLDG 909-1F
Hybrid organic−inorganic perovskite films with the generalformula APbX3 (A = CH3NH3, CH(NH2)2; X = I, Br, Cl)have received significant attention as absorber materials forphotovoltaics. Recent studies have shown that perovskitesolar cells (PSCs) with high efficiencies can be created by mixingdifferent halides or by mixing different organic cations.
A key point in this context is to understand the kinetic andenergetic effects that determine how these ions mix.Here we explain how these materials can be studiedusing in situ grazing incidence X-ray diffraction (GIXD)and how this can be optimized to be able to followthe changes in the samples in real time.In systems where the organic cation is exchanged, we find a continuous shift of the lattice parameter.The relative shift compared to the pure materials is used to quantify the exchange.Whether or not a conversion is possible, as well as the amount of exchanged cations,depends on the halide used.In the case of the interconversion of MAPbI3 and MAPbCl3, we observe a decay of thediffraction peaks of the original perovskite and the emergence of new peakscorresponding to the structure with the alternative halide. Moreover, we determined therelevant time scales of the growth and decay of the perovskite structures.
A. Greco, A. Hinderhofer, M. Dar, A. Ibrahim, N. Arora, J. Hagenlocher, A. Chumakov, M. Grätzel, and F. Schreiber, “Kinetics of ion-exchange reactions in hybrid organic-inorganic perovskite thin films studied by in situ real-time X-ray scattering”, J. Phys. Chem. Lett. (2018), in print.
N. Arora, M. I. Dar, A. Hinderhofer, N. Pellet, F. Schreiber, S. M. Zakeeruddin, and M. Grätzel,
“Perovskite solar cells with CuSCN hole extraction layers yield stabilized efficiencies greater than 20%”, Science 358 (2017) 768.
M. I. Dar, A. Hinderhofer, G. Jacopin, V. Belova, N. Arora, S. M. Zakeeruddin, F. Schreiber, and M.Grätzel, “Function follows form: Correlation between the growth and local emission of perovskite structures and the performance of solar cells”, Adv. Funct. Mater. 27 (2017) 1701433.
Contact: Prof. Steffen Duhm