Highly Emissive Self‐Trapped Excitons in Fully Inorganic Zero‐Dimensional Tin Halides

Abstract

The spatial localization of charge carriers to promote the formation of bound excitons and concomitantly enhance radiative recombination has long been a goal for luminescent semiconductors. Zero‐dimensional materials structurally impose carrier localization and result in the formation of localized Frenkel excitons. Now the fully inorganic, perovskite‐derived zero‐dimensional SnII material Cs4SnBr6 is presented that exhibits room‐temperature broad‐band photoluminescence centered at 540 nm with a quantum yield (QY) of 15±5 %. A series of analogous compositions following the general formula Cs4−xAxSn(Br1−yIy)6 (A=Rb, K; x≤1, y≤1) can be prepared. The emission of these materials ranges from 500 nm to 620 nm with the possibility to compositionally tune the Stokes shift and the self‐trapped exciton emission bands.

Efficient Lone-Pair-Driven Luminescence: Structure–Property Relationships in Emissive 5s2 Metal Halides

“…0D metal halides possess fully isolated octahedral units, which can be bridged by inorganic cations as in Cs 4 SnBr 6 or large organic cations as in (C 4 N 2 H 14 Br) 4 SnBr 6 . 19 , 37 While corner-connected octahedra form many higher-dimensional frameworks, corner-connected 0D clusters are quite rare: no divalent cations exhibit such anions, while only seven compounds are known to exhibit the dimeric [M 2 X 11 ] 5– anion. 67 …”

“…The emission of fully 0D metal halides is based wholly on STEs and is most efficient for the fully isolated octahedra, especially with large organic cations. 19 , 37 …”

“…In contrast, the octahedral MX 6 anion can be found in either inert crystallographic environments, where the site symmetry is essentially cubic, 37 , 88 or in environments where the lone pair is expressed through a trigonal or tetragonal deformation. 19 , 85 , 89 Intriguingly, even the inert MX 6 octahedron exhibits some tendency toward off-centering, with signs of dynamic excited-state structural fluctuations observed in tellurium halides 88 , 90 , 91 and Cs 4 MX 6 .…”

“… 19 , 85 , 89 Intriguingly, even the inert MX 6 octahedron exhibits some tendency toward off-centering, with signs of dynamic excited-state structural fluctuations observed in tellurium halides 88 , 90 , 91 and Cs 4 MX 6 . 37 , 92 The importance of such features in the optical performance will be discussed for the case of 5s 2 metal halides based on Sb 3+ and Sn 2+ .…”

Luminescence of Polybromide Defects in Cs4PbBr6

“…[1][2][3] The family of A 4 BX 6 compounds, so called 0D perovskite, containing isolated octahedra, however, have attracted significant research attention recently due to its unique crystal structure and opto-electronic properties. 4,5 These ternary compounds can be formed by the reaction of the two corresponding binary halides:…”