Large-Stokes-Shifted Infrared-Emitting InAs–In(Zn)P–ZnSe–ZnS Giant-Shell Quantum Dots by One-Pot Continuous-Injection Synthesis

Infrared-emitting materials with a large Stokes shift and minimal reabsorption are technologically important for luminescent solar concentrators and for bioimaging applications. Here, we describe the synthesis of new InAs–In­(Zn)­P–ZnSe–ZnS quaternary giant-shell quantum dots that possess efficient photoluminescence in the near-infrared region. We employ a convenient one-pot, continuous-injection approach to achieve the controlled growth of thick In­(Zn)P shells around small InAs nuclei. The In­(Zn)P shell absorbs strongly across the visible spectrum from 400 to 780 nm and transfers the excitation to the InAs core for emission at 873 nm, hence providing a significant Stokes shift and minimal absorption–emission spectral overlap. Density functional theory calculations reveal a conduction band delocalization and a quasi-type-II band alignment that are responsible for the significant spectral red shifts during shell growth, despite a tiny core size of ca. 3 nm. The resulting quantum dots are neutral colored, contain no regulated heavy metals, and are broadly useful in consumer optoelectronic products and biological applications.