Tin-assisted growth of all-inorganic perovskite nanoplatelets with controllable morphologies and complementary emissions

Abstract

In the present work, a novel Sn-assisted synthetic protocol is developed to control the growth and the optical performance of all-inorganic perovskite nanocrystals (NCs). We systematically elucidate the roles that the Sn⁴⁺ (i.e., SnBr₄ and SnCl₄) and Sn²⁺ (i.e., SnBr₂, SnCl₂ and Sn(OAc)₂) species played in tuning the morphologies and optical properties of the resulting NCs in open air or under Ar atmosphere, respectively. Interestingly, the Sn⁴⁺ cations restrain the growth of the perovskite NCs along a specific plane and consequently lead to the generation of nanoplatelets (NPLs) with thicknesses of a few perovskite unit cell layers, exhibiting the quantum confinement effect. The co-existence of two populations of NCs with different thicknesses contributes to the formation of two well-defined optical absorption bands and photoluminescence (PL) emissions. The unusual disproportionation growth of the perovskite NCs was further confirmed by comparison of NCs grown in open air and under Ar atmosphere, respectively. Perovskite NCs fabricated under Ar atmosphere in the presence of either SnBr₂ or SnCl₂ showed a single PL emission. However, when the reactions were carried out in the open air, dual optical absorbance and PL emissions were observed. Moreover, by adjusting the input of Sn salts in the precursors, the band structure and PL properties can be precisely tuned. The present strategy can be extended to other tetravalent ions such as Ti⁴⁺. We finally employed freshly made dual-emissive CsPbBr₃ perovskite NCs to fabricate a prototype white light-emitting diode (WLED) with a commercially available 365 nm GaN chip.