Lead-Free Semiconductors: Phase-Evolution and Superior Stability of Multinary Tin Chalcohalides
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36 MATERIALS SCIENCE↗
Engineering topics
Roth, Alison N.
Publications and source records attributed to Roth, Alison N..
Designing complex Pb 3 SBr x I 4− x chalcohalides: tunable emission semiconductors through halide-mixing
Quaternary chalcohalides, Pb 3 SBr x I 4− x (1 ≤ x ≤ 3), exhibit tunable photoluminescence emission through halide-mixing with variable amounts of Br − and I − anions in their structure.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Solution-Phase Synthesis and Photoluminescence of Quaternary Chalcohalide Semiconductors
Mixed-metal chalcohalide semiconductors have emerged as promising candidates for photovoltaic applications. However, preparation of these multinary compounds using solution-phase techniques remains particularly challenging compared to traditional solid-state methods. To fully harness their potential, it is desirable to develop synthetic methods that enable control over both the phase purity and dimensionality of chalcohalides. In this work, we report the solution-phase synthesis of Pb 2 SbS 2 I 3 and Pb 2 BiS 2 I 3 quaternary chalcohalides using readily available precursors. Fine tuning of reaction parameters allows for the isolation of rod-like morphologies with tunable diameters and aspect ratios. The quaternary chalcohalides display photoluminescence as an ensemble as well as at the single particle level, as demonstrated using fluorescence microscopy. We further evaluate the relative stability and band gap of Pb 2 SbS 2 I 3 polymorphs and their coloring patterns using electronic structure calculations. The synthetic methods developed here will motivate the study of ever more complex chalcohalides and other multinary semiconductors for new technological applications.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Alkaline-Earth Chalcogenide Nanocrystals: Solution-Phase Synthesis, Surface Chemistry, and Stability
Increasing demand for effective energy conversion materials and devices has renewed interest in semiconductors comprised of earth-abundant and biocompatible elements. Alkaline-earth sulfides doped with rare earth ions are versatile optical materials. However, relatively little is known about controlling the dimensionality, surface chemistry, and inherent optical properties of the undoped versions of alkaline-earth monoand polychalcogenides. Here, we describe the colloidal synthesis of alkaline-earth chalcogenide nanocrystals through the reaction of metal carboxylates with carbon disulfide or selenourea. Systematic exploration of the synthetic phase space allows us to tune particle sizes over a wide range using a mixture of commercially available carboxylate precursors. Solid-state NMR spectroscopy confirms the phase purity of the selenide compositions. Surface characterization reveals that bridging carboxylates and amines preferentially terminate the surface of the nanocrystals. While these materials are colloidally stable in the mother solution, the selenides are susceptible to oxidation over time, eventually degrading to selenium metal through polyselenide intermediates. As part of these investigations, we have developed the colloidal syntheses of barium di- and triselenides, two among few reported nanocrystalline alkaline-earth polychalcogenides. Electronic structure calculations reveal that both materials are indirect band gap semiconductors. The colloidal chemistry presented here may enable the synthesis of more complex, multinary chalcogenide materials containing alkaline-earth elements.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗