Abstract
The photovoltaic perovskite, methylammonium lead triiodide [CH3NH3PbI3 (MAPbI3)], is one of the most efficient materials for solar energy conversion. Various kinds of chemical and physical modifications have been applied to MAPbI3 towards better understanding of the relation between composition, structure, electronic properties and energy conversion efficiency of this material. Pressure is a particularly useful tool, as it can substantially reduce the interatomic spacing in this relatively soft material and cause significant modifications to the electronic structure. Application of high pressure induces changes in the crystal symmetry up to a threshold level above which it leads to amorphization. Here, a detailed structural study of MAPbI3 at high hydrostatic pressures using Ne and Ar as pressure transmitting media is reported. Single-crystal X-ray diffraction experiments with synchrotron radiation at room temperature in the 0-20 GPa pressure range show that atoms of both gaseous media, Ne and Ar, are gradually incorporated into MAPbI3, thus leading to marked structural changes of the material. Specifically, Ne stabilizes the high-pressure phase of NexMAPbI3 and prevents amorphization up to 20 GPa. After releasing the pressure, the crystal has the composition of Ne0.97MAPbI3, which remains stable under ambient conditions. In contrast, above 2.4 GPa, Ar accelerates an irreversible amorphization. The distinct impacts of Ne and Ar are attributed to differences in their chemical reactivity under pressure inside the restricted space between the PbI6 octahedra.
Highlights
methylammonium lead triiodide [CH3NH3PbI3 (MAPbI3) is currently considered as one of the most promising compounds in photovoltaic technologies for making cheap and highly efficient solar cells (Green et al, 2014; Weber et al, 2015)
In different experiments the onset of the amorphization has been observed under different pressures, and the pressure transmitting medium (PTM) could be considered as a factor affecting the pressure-induced transformation of MAPbI3 (Fig. 1)
Room-temperature (293 K) high-pressure X-ray diffraction (XRD) data were collected at the ID27 High Pressure Beamline of the European Synchrotron Radiation Facility (ESRF) in Grenoble
Summary
MAPbI3 is currently considered as one of the most promising compounds in photovoltaic technologies for making cheap and highly efficient solar cells (Green et al, 2014; Weber et al, 2015). A recently published extended review (Luet al., 2017) on the pressure-induced evolution of the structure and the physical properties of organic–inorganic halide perovskites demonstrates a poor reproducibility of the changes. In different experiments the onset of the amorphization has been observed under different pressures, and the pressure transmitting medium (PTM) could be considered as a factor affecting the pressure-induced transformation of MAPbI3 (Fig. 1). Such an effect has already been observed in organic compounds (Zakharov et al, 2016) and in some minerals (Ardit et al, 2014; Sato et al, 2013; Gunka et al, 2015; Lobban et al, 2002). The pressure-induced phase of Ne0.97MAPbI3 remained stable and highly crystalline after decompression
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