Seed-Mediated Synthesis of Photoluminescent Cu–Zn–In–S Nanoplatelets

Ternary and quaternary colloidal nanocrystals (NCs) based on I-III-VI group semiconductors are promising low-toxic luminescent materials attracting huge interest as alternatives to cadmium-and leadchalcogenide-based NCs. Despite significant progress in the synthesis of three-dimensionally confined quantum dots based on I-III-VI semiconductors with intensive photoluminescence (PL) in a broad spectral range, all attempts to prepare one-dimensionally confined nanoplatelets (NPLs) or nanosheets have resulted in rather nonemitting two-dimensional (2D) NCs. Since 2D NCs of the II-VI group exhibit unique anisotropic optical properties, exploring synthetic strategies to obtain 2D I-III-VI-based NPLs might also reveal interesting optical and electronic features. In this work, we demonstrate the synthesis of luminescent In-rich Cu-Zn-In-S (CZIS) NPLs using a one-pot approach. The synthesis includes the formation of Cu-In-S NPLs from In2S3 seeds, followed by the incorporation of zinc to form quaternary NPLs with improved stability and optical properties. The synthetic strategy implemented results in the formation of -1 nm thick NPLs with lateral sizes of -30 x 10 nm2 and a tetragonal crystal structure. As-synthesized NPLs are stable at ambient conditions and demonstrate PL in the range of 700-800 nm with a large Stokes shift. An additional shell of ZnS grown on CZIS NPLs resulted in the enhancement of their PL quantum yield reaching 29%.