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

Abstract

Non-isovalent ternary and quaternary semiconductors (i.e., having two or more cations with different valence) 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 for 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 the well-studied PbS nanocrystals highlighting their potential for devices such as solar cells, (mid-)infrared photodetectors, and near-infrared bio-imaging systems. ASSOCIATED CONTENTSupporting data to the article (Figures S1-S15), containing quantifications of EDX spectra, extraction of lattice constants, TEM images, size distributions and additional XRD patterns for Ag-Sb-Se nanocrystals; crystal structure of Cu3SbSe4; absorption spectra and Tauc analysis of various I-V-VI nanocrystals. This material is available free of charge via the Internet at http://pubs.acs.org.

Synthesis of small Ag–Sb–Te nanocrystals with composition control

“…In particular, Ag and Sb exhibit very different electronegativities, and Sb 3+ is known to easily undergo disproportionation 36 . Furthermore, while a number of synthetic protocols exist for ternary I-V-VI sulfides [37][38][39] and selenides 35,[40][41][42] , synthesis of I-V-VI tellurides poses additional challenges due to a high reactivity of Te-precursors and decreased stability 32 . Since amide-promoted syntheses have enabled size and composition control of various nanocrystals including silver chalcogenides 34 , I-III-VI selenides 43 and tellurides 2 , I-V-VI selenides 42 and GeTe 30 , we explore an amide-promoted synthesis for I-V-VI tellurides.…”

“…Here, we present an amide-promoted synthesis, which yields small Ag x Sb 1-x Te 1.5-x nanocrystals with tunable composition between Ag 0.3 Sb 0.7 Te 1.2 and Ag 0.6 Sb 0.4 Te 0.9 (i.e., x ranges from 0.3 to 0.6). The choice of synthetic approach is motivated by previous success in preparing various chalcogenide nanocrystals 2,34,35 . Due to improved nucleation rates, amidepromoted synthesis typically provides small size nanocrystals and quantitative reaction yields at short reaction times.…”

High-Performance Inorganically Connected CuInSe2 Nanocrystal Thin-Film Transistors and Integrated Circuits Based on the Solution Process of Colloidal Synthesis, Ligand Exchange, and Surface Treatment

“…12,13 NCs made of I−III−VI semiconductors, including CuInS-(Se) 2 , AgInS 2 , CuGaS 2 , and so forth, have attracted broad interest, owing to their diverse properties and low toxicity compared with binary II−VI or IV−VI semiconductor materials. 14,15 As an outstanding option, CuInSe 2 shows great promise because of its narrow direct band gap of ∼1.04 eV, large calculated exciton Bohr radius of ∼10.6 nm, and high absorption coefficient of ∼10 5 cm −1 . 16,17 size-, shape-, and composition-dependent electronic and optical properties, it is possible to achieve a desired carrier type, concentration, and mobility for CuInSe 2 NCs for thinfilm electronic devices.…”

Phase Transitions in Germanium Telluride Nanoparticle Phase-Change Materials Studied by Time-Resolved X-Ray Diffraction

“…For example, localized surface plasmon resonances have been reported for crystalline GeTe nanoparticles, 20 and a bandgap increase has been observed. 21,22 Furthermore, several studies on the sizedependent shift of the crystallization temperature T C,1 have been published, as shown for GeTe in Tab. I.…”