Regensburg 2016 – scientific programme
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DS: Fachverband Dünne Schichten
DS 29: Hybrid and Perovskite Photovoltaics III
(Joint session of CPP, DS and HL, organized by DS)
DS 29.1: Talk
Wednesday, March 9, 2016, 09:30–09:45, H11
Impact of Preparation Conditions on the Ionization Energy and Electronic Structure of CH3NH3PbI3 Perovskites — •Jennifer Emara1, Tobias Schnier1, Neda Pourdavoud2, Thomas Riedl2, Klaus Meerholz1, and Selina Olthof1 — 1University of Cologne, Institute for Physical Chemistry, Luxemburger Straße 116, 50939 Köln, Germany — 2Institute of Electronic Devices, University of Wuppertal, Rainer-Grunter-Straße 21, 42119 Wuppertal, Germany
Hybrid organic/inorganic halide perovskites have lately been a topic of great interest in the field of solar cell applications, with the potential to achieve device efficiencies exceeding other thin film device technologies. Yet, large variations in device efficiency and basic physical properties are reported. This is due to unintentional variations during film processing, which have not been systematically investigated so far. We therefore conducted an extensive study of the electronic structure of a large number of CH3NH3PbI3 perovskite films produced by different preparation methods and by varying precursor ratios. We show that variations in film stoichiometry lead to vast changes in the density of states (DOS), and changes in ionization energy, which can be intentionally tuned by almost 1 eV. Using x-ray diffraction measurements, we find the variations in film stoichiometry are not due to the formation of separate phases, but that interstitials and vacancies are homogeneously distributed within the material. Implementing the prepared perovskite layer materials in solar cells, we find a clear correlation between the changes in DOS with the overall power conversion efficiency.