Guanidinium and mixed Cesium-Guanidinium Tin(II) Bromides: Effects of Quantum Confinement and Out-of-Plane Octahedral Tilting

Olga Nazarenko (1, 2) , Martin Kotyrba (1, 2) , Sergii Yakunin (1, 2) , Michael Wörle (1) , Bogdan Benin (1, 2) , Gabriele Rainò (1, 2) , Frank Krumeich (1) , Mikaël Kepenekian (3) , Jacky Even (4) , Claudine Katan (3) , Maksym V Kovalenko (1, 2)

1 ETH Zürich - Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich]
2 EMPA - Swiss Federal Laboratories for Materials Science and Technology [Dübendorf]
3 ISCR - Institut des Sciences Chimiques de Rennes
4 FOTON - Institut des Fonctions Optiques pour les Technologies de l'informatiON

Hybrid organic–inorganic main-group metal halide compounds are the subject of intense research owing to their unique optoelectronic characteristics. In this work, we report the synthesis, structure, and electronic and optical properties of a family of hybrid tin (II) bromide compounds comprising guanidinium [G, C(NH2)3+] and mixed cesium–guanidinium cations: G2SnBr4, CsGSnBr4, and Cs2GSn2Br7. G2SnBr4 has a one-dimensional structure that consists of chains of corner-sharing [SnBr5]2– square pyramids and G cations situated in between the chains. Cs+ exhibits a pronounced structure-directing effect where a mixture of Cs+ and G cations forms mono- and bilayered two-dimensional perovskites: CsGSnBr4 and Cs2GSn2Br7. Furthermore, the flat shapes of the guanidinium cations induce anisotropic out-of-plane tilts of the [SnBr6]4– octahedra in the CsGSnBr4 and Cs2GSn2Br7 compounds. In G2SnBr4, the Sn lone pair is highly stereoactive and favors non-octahedral, that is, square pyramidal coordination of Sn(II). G2SnBr4 exhibits bright broad-band emission from self-trapped excitonic states, owing to its soft lattice and electronic localization. This emission in G2SnBr4 is characterized by a photoluminescence (PL) quantum yield of 2% at room temperature (RT; 75 ± 5% at 77 K) and a fast PL lifetime of 18 ns at room temperature.

Domaines: Matériaux

Olga Nazarenko, Martin Kotyrba, Sergii Yakunin, Michael Wörle, Bogdan Benin, et al.. Guanidinium and mixed Cesium-Guanidinium Tin(II) Bromides: Effects of Quantum Confinement and Out-of-Plane Octahedral Tilting. Chemistry of Materials, 2019, 31 (6), pp.2121-2129. ⟨10.1021/acs.chemmater.9b00038⟩. ⟨hal-02019936⟩