Wargulski, D.R.; Xu, K.; Hempel, H.; Flatken, M.; Albrecht, S.; Abou-Ras, D.: Relationship Between Annealing Temperature and the Presence of PbI2 Platelets at the Surfaces of Slot-Die Coated Triple-Halide Perovskite Thin Films. ACS Energy Letters 15 (2023), p. 41516–41524
10.1021/acsami.3c07692
Open Access Version
Abstract:
We investigated triple-halide perovskite (THP) absorber layers, fabricated by slot-die coating with subsequent annealing step. We found the solar cell power conversion efficiency suffers by increasing the annealing temperature from 125 to 170 °C, mainly via losses in the open-circuit voltage (Voc) and the fill factor (FF). To understand the mechanisms behind these losses, extensive characterizations were performed on THP thin films and the completed solar cell stacks. Correlative scanning electron microscopy analyses, i.e., electron back scatter diffraction, energy-dispersive x-ray spectroscopy, and cathodoluminescence confirmed the presence of PbI2 platelets on the THP thin films. Moreover, the area fraction of the PbI2 on the film surfaces increased with the annealing temperature. We explain the deteriorated device performance by increased series resistances and interface recombination caused by PbI2, decreasing the Voc and the FF. Thus, the correlative analyses provided insight into microscopic origins of the efficiency losses. A corresponding model is presented on how the precipitates affect the photovoltaic parameters.