Structural and optical properties of Cs2AgBiBr6 double perovskite

Journal article

We present a comprehensive study of the relationship between the crystal structure and optoelectronic properties of the double perovskite Cs2AgBiBr6, which has emerged as a promising candidate for photovoltaic devices. On the basis of single-crystal/powder X-ray diffraction and neutron powder diffraction, we have revealed the presence of a structural phase transition at Ts ≈ 122 K between the room-temperature cubic structure (space group Fm3̅m) and a new low-temperature tetragonal structure (I4/m). From reflectivity measurements we found that the peak exciton energy Eex ≈ 2.85 eV near the direct gap shifts proportionally to the tetragonal strain, which is consistent with the Eex being primarily controlled by a rotational degree of freedom of the crystal structure, thus by the angle Bi−Ag−Br. We observed the time-resolved photoluminescence kinetics and we found that, among the relaxation channels, a fast one is mainly present in the tetragonal phase, suggesting that its origin may lie in the formation of tetragonal twin domains.

Authors: Schade, L; Wright, A; Johnson, R; Dollmann, M; Wenger, B

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Chemical Society
• Journal: ACS Energy Letters
• Volume: 4
• Issue: 1
• Pages: 299-305
• Publication date: 2018-12-19
• Acceptance date: 2018-12-19
• DOI: 10.1021/acsenergylett.8b02090
• EISSN: 2380-8195
• Language: English