Abstract
Organic-inorganic coupling in the hybrid lead-halide perovskite is a central issue in rationalizing the outstanding photovoltaic performance of these emerging materials. Here, we compare and contrast the evolution of the structure and dynamics of hybrid CH3NH3PbBr3 and inorganic CsPbBr3 lead-halide perovskites with temperature, using Raman spectroscopy and single-crystal x-ray diffraction. Results reveal a stark contrast between their order-disorder transitions, which are abrupt for the hybrid whereas smooth for the inorganic perovskite. X-ray diffraction observes an intermediate incommensurate phase between the ordered and the disordered phases in CH3NH3PbBr3. Low-frequency Raman scattering captures the appearance of a sharp soft mode in the incommensurate phase, ascribed to the theoretically predicted amplitudon mode. Our work highlights the interaction between the structural dynamics of organic cation CH3NH3+ and the lead-halide framework, and unravels the competition between tendencies for the organic and inorganic moieties to minimize energy in the incommensurate phase of the hybrid perovskite structure.
| Original language | English |
|---|---|
| Article number | 042401(R) |
| Number of pages | 6 |
| Journal | Physical Review Materials |
| Volume | 1 |
| Issue number | 4 |
| DOIs | |
| Publication status | Published - 27 Sept 2017 |
Funding
Y.G. acknowledges financial support from the Keck Foundation. O.Y. acknowledges funding by the FP7 People program under the project Marie Curie Grant No. IOF-622653. M.A.P. acknowledges financial support from the Brazilian agencies CNPq, CAPES, FAPEMIG, and Brazilian Nanocarbon Institute of Science and Technology (INCT-Nanocarbono). X-ray diffraction was performed in the Shared Materials Characterization Laboratory at Columbia University. Use of the Shared Materials Characterization Laboratory was made possible by funding from Columbia University.