Composition- and Size-Controlled I–V–VI Semiconductor Nanocrystals

Nonisovalent ternary and quaternary semiconductors (i.e., having two or more cations with different valence electrons) have unique structural and electronic properties that are leveraged in photovoltaic, thermoelectric, and phase-change memory devices. Making these complex semiconductors in the form of colloidal nanocrystals imparts size-dependent properties and solution processability. Here, we present results on I–V–VI group colloidal nanocrystals. We focus on achieving sub-10 nm sizes for a wide range of I–V–VI selenide nanocrystals, including AgSbSe2, AgSb2Se3, CuSbSe2, Cu3SbSe4, AgBiSe2, and CuBiSe2. To highlight one possible application of these I–V–VI colloidal nanomaterials, we analyze the optical absorption and show that through composition and size control, this class of materials offers bandgaps in the mid- to near-IR. Absorption coefficients of AgSbSe2, CuSbSe2, and Cu3SbSe4 nanocrystals are on par with or higher than those of the well-studied PbS nanocrystals, highlighting their potential for devices such as solar cells, (mid-)­infrared photodetectors, and near-infrared bio-imaging systems.