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

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. Komplett anorganisches Perowskit‐artiges nulldimensionales Cs4SnBr6 zeigt bei Raumtemperatur aufgrund von selbstfangenden Exzitonen eine breite Photolumineszenzbande um 540 nm mit einer Quantenausbeute von 15±5 % (298 K; nahe 100 % bei 200 K) und einer großen Stokes‐Verschiebung von ca. 1.2 eV. Für die Reihe der Zusammensetzungen Cs4−xAxSn(Br1−yIy)6 (A=Rb, K; x≤1, y≤1) verschieben sich die Emissionsmaxima von 500 nm bis 620 nm.