Berlin 2015 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 84: Focus Session (CPP with HL): Hybrid photovoltaics and perovskites II
HL 84.7: Vortrag
Donnerstag, 19. März 2015, 17:15–17:30, C 130
Unbalanced Charge Distribution Inside a Perovskite-Sensitized Solar Cell in Real Space — •Victor W. Bergmann1, Stefan A.L. Weber1, F. Javier Ramos2, Mohammad Khaja Nazeeruddin3, Michael Grätzel3, Dan Li1, Anna L. Domanski1, Ingo Lieberwirth1, Shahzada Ahmad2, and Rüdiger Berger1 — 1Max Planck Institute for Polymer Research, Mainz, Germany — 2Abengoa Research, Seville, Spain — 3Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
Solar cells based on perovskite light absorbing materials reached power conversion efficiencies >20%. Today, the knowledge about the local charge generation processes inside these solar cells is limited. We prepared smooth cross sections by means of focused ion beam milling such that the full structure and functionality of the devices were preserved [1]. This way, the internal interfaces between the different materials in the cell are accessible for frequency modulation Kelvin Probe Force Microscopy (FM-KPFM). Upon illumination under short-circuit conditions, holes accumulate in front of the hole transport layer, which is proof of an unbalanced charge transport. This potential barrier reduces the charge transfer towards the electrode. Furthermore after light illumination, we measured remaining charges inside the active device area. These charges were attributed to traps in the material. In conclusion, the FM-KPFM method allows us not only to map the local contact potential variation but also to correlate it with the local structure of the functional layers.
[1] Bergmann et al. Nature Communications 5, 5001 (2014).