Pressure-Induced Phase Transition versus Amorphization in Hybrid Methylammonium Lead Bromide Perovskite

Abstract

The crystal structure of the CH 3 NH 3 PbBr 3 perovskite has been investigated under high-pressure conditions by synchrotron-based powder X-ray diffraction. We found that after the previously reported phase transitions in CH 3 NH 3 PbBr 3 (Pm3̅ m→Im3̅ →Pmn2 1 ), which occur below 2 GPa, there is a third transition to a crystalline phase at 4.6 GPa. This transition is reported here for the first time contradicting previous studies, which reported amorphization of CH 3 NH 3 PbBr 3 between 2.3 and 4.6 GPa. Our X-ray diffraction measurements show that CH 3 NH 3 PbBr 3 remains crystalline up to at least 7.6 GPa, the highest pressure covered by experiments. The new high-pressure phase is also described by the space group Pmn2 1 ; however, the transition involves abrupt changes in the unit-cell parameters and a 3% decrease of the unit-cell volume. Our conclusions are confirmed by optical-absorption experiments, by visual observations, and by the fact that pressure-induced changes up to 10 GPa are reversible. The optical studies also allow for the determination of the pressure dependence of the band-gap energy, which is discussed using the structural information obtained from X-ray diffraction.

Bandgap Pressure Coefficient of a CH3NH3PbI3 Thin Film Perovskite

“…It is also worth noting that the blue-shift caused by octahedral tilting is larger at 80 K (54 meV) than at 40 K (39 meV), which supports the effect of the temperature on the magnitude of octahedral distortion. The observed behavior of MAPbI 3 thin films under pressure at 40 and 80 K is similar to that of single crystals compressed at room temperature with the initial red-shift of the PL energy positions followed by a blue-shift. ,, Similar behavior has been also observed in room-temperature pressure studies of other halide perovskites and can be regarded as an indicator of the phase transition occurring in the studied pressure range. − In our case, the observed blue-shift may also be a phase transition marker, but phase transition studies require structural confirmation and are not the aim of this work. At 120 K, the bandgap red-shift is observed up to 3.99 GPa (Figure c,f), while the bandgap blue-shift does not occur in the studied pressure range.…”

“… 19 , 20 , 26 Similar behavior has been also observed in room-temperature pressure studies of other halide perovskites and can be regarded as an indicator of the phase transition occurring in the studied pressure range. 38 − 40 In our case, the observed blue-shift may also be a phase transition marker, but phase transition studies require structural confirmation and are not the aim of this work. At 120 K, the bandgap red-shift is observed up to 3.99 GPa ( Figure 1 c,f), while the bandgap blue-shift does not occur in the studied pressure range.…”

Structural and optical properties of methylhydrazinium lead bromide perovskites under pressure

“…Similar, almost pressure-independent behaviour of E g has recently been reported for analogous 3D perovskite MAPbBr 3 under pressure above 5 GPa. 32 However, in this material a comparable large increase of E g is realised through a sequence of three phase transitions, while in MHyPbBr 3 it occurs in one step.…”

Blue light emission enhancement and robust pressure resistance of gallium oxide nanocrystals

“…3d, and decrease in signal intensity, which is probably due to pressure-driven disorder in the crystal structure. 41 This trend promotes an increase in defects, giving rise to a slow decrease in emission. The suppression of oxygen vacancy defect formation will lead to a decrease in the distance ( r ) between the acceptor and donor in the DAP complex, 27,38 and hence a shift in DAP emission towards higher energy (Fig.…”