Stefan Weber1,2,Ilka Hermes1,3,Yenal Yalcinkaya1,2,Pascal Rohrbeck1,Konstantinos Bidinakis1,Rüdiger Berger1
Max Planck Institute for Polymer Research1,Johannes Gutenberg University2,Leibniz Institute for Polymer Research3
Stefan Weber1,2,Ilka Hermes1,3,Yenal Yalcinkaya1,2,Pascal Rohrbeck1,Konstantinos Bidinakis1,Rüdiger Berger1
Max Planck Institute for Polymer Research1,Johannes Gutenberg University2,Leibniz Institute for Polymer Research3
Perovskite solar cells have electrified the solar cell research community with astonishing performance and surprising material properties. However, the widespread commercialization of perovskites in solar cells and other optoelectronic applications still requires a more detailed knowledge about fundamental material properties. My group is specialized in the investigation of these properties on nanometer length scales using scanning force microscopy [1-4].<br/>In 2016, we discovered a distinct nanoscale stripe domain structure in MaPbI<sub>3</sub> perovskite crystals that is characteristic for ferro-elastic twin domains [1]. Using a combination of piezoresponse force microscopy (PFM) and photoluminescence microscopy, we found that this domain structure leads to an anisotropic charge transport across the crystal [2]. To utilize this effect in devices, a precise control of the domain configuration would be desirable. To this end, we explored the possibilities of both physical and chemical strain engineering [3]. Next to these intrinsic properties of perovskites, the specific interactions at the various interfaces in devices are of critical importance. To visualize the functionality of different layers, we developed a method to prepare smooth cuts through a solar cell device. We subsequently map the potential distribution across the device using time-resolved Kelvin probe force microscopy (tr-KPFM) [4,5]. We could show that the formation and release of ionic interface charges determine the time scales for current-voltage hysteresis in perovskite solar cells. Our results highlight that precise control over interfaces in perovskite solar cells is the key, not only for controlling and suppressing hysteresis but also for their long-term stability in perovskite solar cells.<br/><br/>[1] Hermes et al. J. Phys. Chem C, <b>120</b>(10), 5724 (2016).<br/>[2] Hermes et al. Energy Environ. Sci. <b>13</b>, 4168 (2020).<br/>[3] https://arxiv.org/abs/2205.00381.<br/>[4] Weber et al. Energy Environ. Sci., <b>11</b>, 2404 (2018).<br/>[5] Hermes et al. J. Phys. Chem. Lett., <b>9</b>, 6249 (2018).