Berlin 2015 – scientific programme

Parts | Days | Selection | Search | Updates | Downloads | Help

CPP: Fachverband Chemische Physik und Polymerphysik

CPP 68: Focus Session Hybrid Photovoltaics and Perovskites (joint session CPP, HL)

CPP 68.7: Talk

Thursday, March 19, 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).