Berlin 2015 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 101: Scanning Probe Techniques: AFM

O 101.9: Vortrag

Freitag, 20. März 2015, 12:30–12:45, MA 144

A Closer Look into Operating Perovskite-Sensitized Solar Cells — •Stefan Weber¹, Victor Bergmann¹, Javier Ramos², Mohammad Nazeeruddin³, Michael Graetzel³, Shazada Ahmad², and Ruediger Berger¹ — ¹MPI for Polymer Research, Mainz, Germany — ²Abengoa Research, Seville, Spain — ³EPFL, Lausanne, Switzerland

Solar cells based on novel hybrid organic-inorganic halide perovskites have recently reached power conversion efficiencies comparable to silicon solar cells. Nevertheless, the exact charge generation mechanism in perovskites is still unclear. The aim of our study is to apply scanning probe microscopy (SPM) for measuring the electrical potential in the different layers of the device under working conditions. Therefore, a SPM setup was equipped with a sample illumination and placed in an inert atmosphere to avoid photo-oxidation of the sensitive materials. We prepared smooth cross sections of the solar cell by means of focused ion beam milling. This way, the internal interfaces between the different materials in the fully functional device were accessible for frequency modulation Kelvin Probe Force Microscopy (FM-KPFM). Our measurements revealed that the investigated perovskite devices have an internal potential distribution that represents a p-i-n type junction solar cell. Upon illumination under short-circuit conditions, we found an unbalanced charge transport inside the device with holes accumulating in the preovskite layer. These results are important for understanding the physics of perovskite solar cells [Bergmann, V.W. et al (2014); Nature Comm. 5, 5001].