Pressure response of decylammonium-containing 2D iodide perovskites

Abstract

Manipulation by external pressure of the optical response of 2D Metal Halide Perovskites (MHPs) is a fascinating route to tune their properties and promote the emergence of novel features. We investigate here DA₂PbI₄ and DA₂GeI₄ (DA = decylammonium) perovskites in the pressure range up to ∼12 GPa by X-ray powder diffraction, absorption, and photoluminescence spectroscopy. Although the two systems share a similar structural evolution with pressure, the optical properties are rather different and influenced by Pb or Ge. DA₂PbI₄ shows a progressive red shift from 2.28 eV (P = 0 GPa) to 1.64 eV at 11.5 GPa, with a narrow PL emission, whereas DA₂GeI₄, changes from a non-PL system at ambient pressure to a clear broadband emitter centered around 730 nm with an intensity maximum at about 3.7 GPa. These results unveil the role of the central atom on the nature of emission under pressure in 2D MHPs containing a long alkyl chain.

Keywords: Engineering; Materials characterization; Materials chemistry; Materials physics.

Graphical abstract

Figure 1

Diffraction data of DA₂PbI₄ (A–C) (A) XRD patterns (λ = 0.495 Å) as a function of pressure (reported in GPa on the right) for DA₂PbI₄; (B) and (C) highlights selected intervals of the pattern to better shown the evolution of the (001) and (002) reflections as a function of pressure.

Figure 2

Pressure dependence of structural parameters of DA₂PbI₄ (A and B) Pressure dependence of the cell parameters a, b, c (A) and of the cell volume (B) for DA₂PbI₄. The c axis of the orthorhombic cell was halved. The dashed line marks the transition from the orthorhombic to the monoclinic cell. Subscripts 1 and 2 refer to the two monoclinic phases. Error bars are smaller than the symbol.

Figure 3

Absorption spectroscopy results of DA₂PbI₄ (A and B) (A) absorption spectra as a function of pressure for DA₂PbI₄; (B) trend of the absorption edge extracted from the spectra as a function of pressure.

Figure 4

Photoluminescence results of DA₂PbI₄ (A and B) (A) PL spectra as a function of pressure for DA₂PbI₄; (B) trend of the peak position of the PL data as a function of pressure.

Figure 5

Diffraction data of DA₂GeI₄ (A–C) (A) XRD patterns (λ = 0.495 Å) as a function of pressure (reported in GPa on the right) for DA₂GeI₄; (B) and (C) highlights selected intervals of the pattern to better show the evolution of the (001) and (002) reflections as a function of pressure.

Figure 6

Pressure dependence of structural parameters of DA₂GeI₄ (A and B) Pressure dependence of the cell parameters a, b, c (A) and of the cell volume (B) for DA₂GeI₄. The c axis of the orthorhombic cell was halved. The dashed line marks the transition from the orthorhombic to the monoclinic cell. Error bars are smaller than the symbol.

Figure 7

Absorption spectroscopy results of DA₂GeI₄ (A and B) (A) absorption spectra as a function of pressure for DA₂GeI₄. The peak at 633 nm is from the HeNe calibration laser; (B) trend of the absorption edge extracted from the spectra as a function of pressure.

Figure 8

Photoluminescence results of DA₂GeI₄ (A and B) (A) PL data under compression for DA₂GeI₄. Oscillations above ∼800 nm are caused by detector etaloning; (B) PL data as a function of temperature for DA₂GeI_4.