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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 105: Focus: In-situ probes toward better understanding of hybrid halide perovskites (PhD symposium) II (joint session CPP/AKjDPG)
CPP 105.7: Vortrag
Freitag, 20. März 2020, 11:45–12:00, ZEU 222
Energy-Level Alignment of Formamidinium Tin Iodide with Organic Contact Materials — •Jonas Horn, Pascal Schweitzer, and Derck Schlettwein — Justus Liebig University Gießen, Institute of Applied Physics
The alignment of energy levels at the interfaces of a perovskite absorber with adjacent hole- and electron-transporting materials affects the formation of space-charge regions and interfacial recombination. These have consequences for charge transport in the layers and for the efficiency of devices. To analyze such alignment we used Kelvin-probe force microscopy (KPFM). This study is focused on formamidinium tin iodide (FASnI3) as perovskite absorber, which avoids the toxicity problems of lead and is known to yield the highest power conversion efficiencies amongst all lead-free perovskite absorbers. The most common solar cell geometry for FASnI3 implements C60 as electron-transporting material, which is prepared onto the perovskite by physical vapor deposition (PVD). Intermittently to PVD, we used KPFM to simultaneously monitor morphology and work function of C60 during its growth on FASnI3. We show that a sufficiently high deposition rate is needed to avoid island formation of C60 and obtain a homogeneously covering film with constant work function. We further show that the width of the space charge layer in C60 is larger than the film thickness often implemented in perovskite solar cells. A band bending in the range of 300 meV is observed and consequences for prospective device operation are discussed.