Revealing the Role of Caged Cations in Hybrid Perovskites

Revealing the Role of Caged Cations in Hybrid Perovskites

Scientific Achievement
Neutron diffraction reveals that caged MA+ cations become disordered as the temperature is raised beyond 130K to induce a phase transition (orthorhombic to tetragonal) in novel hybrid perovskite materials used for solar cells, affecting their optoelectronic properties. Inset shows 3mm CH3NH3PbBr3 single crystals grown at CNMS. (hi-res image)

Neutron diffraction and theory reveal that disordering of the caged organic cations in hybrid perovskites (HPs) induces a structural phase transition that improves their optoelectronic properties.

Significance and Impact

HPs exhibit promising optoelectronic properties, but an understanding of how organic cation ordering affects their performance has been lacking.

Research Details

- Neutron and X-ray diffraction studies reveal that methylammonium (MA+) cations become disordered in HPs, causing a structural phase transition and anomalous photoluminescence (PL).

- Density Functional Theory calculations explain that the anomalous increase in photoluminescence (PL) intensity is a result of the reduction of defect density and increased dielectric screening, both caused by increasing disorder of the caged MA+ cations in HPs.

B. Yang, W. Ming, M-H. Du, J. Keum, A. A. Puretzky, C. M. Rouleau, J. Huang, D. B. Geohegan, X. Wang, and K. Xiao, "Real-time observation of order-disorder transformation of organic cations induced phase transition and anomalous photoluminescence in hybrid perovskites," Adv. Mater. (2018).  DOI: 10.1002/adma.201705801

CNMS Researchers