Enhanced photoconversion efficiency in cesium-antimony-halide perovskite derivatives by tuning crystallographic dimensionality

Lead-based perovskites have reached prominence in optoelectronic and photovoltaic research, yet their toxicity has prompted the search for alternative lead-free compounds. All-inorganic antimony-/bismuthhalide perovskite derivatives have been identified as a promising class of materials. Despite attractive bulk optoelectronic properties, their optoelectronic device performance has been lagging behind. Here we examine one of their most promising embodiments, the all-inorganic cesium-antimony-halide system. Through solution-based halide mixing, we achieve its structural conversion from a zero-dimensional to a layered phase at processing temperatures <150 degrees C, i.e., much lower than those relied upon in the prior literature (>= 230 degrees C) of all-inorganic cesium-antimony halides. In order to evaluate the technological significance of this finding, we integrate our layered films into a sandwich-type device structure, and characterize their external quantum efficiency and photovoltaic behavior. We find that the structural conversion leads to a considerable enhancement in the optoelectronic device performance. Additionally, photocurrent-power characterization and Hall effect measurements reveal that this performance enhancement is brought about by an improvement in charge carrier transport, which can be exploited due to the unoriented nature of our low-temperature-processed layered films. Such performance boost and mechanistic insight constitute an important step in realizing the full potential of these (and related) compounds for their application in lead-free optoelectronic and photovoltaic devices, e.g., for top-cell in tandem photovoltaics, indoor photovoltaics, and photodetectors. (C) 2020 Elsevier Ltd. All rights reserved.