Synthesis and Characterization of Zintl-Phase BaCd<sub>2</sub>P<sub>2</sub> Quantum Dots for Optoelectronic Applications
Matthew P. Hautzinger, Shaham Quadir, Benjamin Feingold, Reilly Seban, Arianna J. Thornton, Nikita S. Dutta, Andrew G. Norman, Ian A. Leahy, Muhammad Rubaiat Hasan, Kirill Kovnir, Obadiah G. Reid, Bryon W. Larson, Joseph M. Luther, Matthew C. Beard, Sage R. Bauers
Abstract
High Resolution Image Download MS PowerPoint Slide We demonstrate the growth of size-controlled, high optical quality Zintl-phase BaCd 2 P 2 colloidal quantum dots (QDs), an emerging semiconductor absorbing/emitting in the red and predicted to have favorable defect chemistry. The QDs are grown via hot injection of a phosphorus precursor into a solution of solubilized Ba and Cd precursors. The absorbance and photoluminescence (PL) are tunable via growth temperature and show a bandgap ranging from 1.47 to 1.81 eV, depending on the size, which ranges from 3 to 9 nm based on electron microscopy. Selected area electron diffraction is used to determine that the BaCd 2 P 2 QDs crystallize in the P 3̅ m 1 space group, same as the bulk material. Raman spectroscopy, powder X-ray diffraction, and X-ray fluorescence studies further confirm that BaCd 2 P 2 QDs match those of the crystalline phase bulk material. The high optoelectronic quality is assessed by quantification of long-lived photoexcited carriers (∼160 ns average weighting), as determined by time-resolved PL spectroscopy, and bright red visible emission (∼21% PL quantum yield) despite no complex surface passivation. Furthermore, a demonstration of thin-film fabrication is shown via a solid state ligand exchange protocol. This synthetic protocol enables researchers to explore and utilize BaCd 2 P 2 Zintl-phase QDs, as well as adjacent compositions, for a variety of optoelectronic applications enabled by their semiconducting properties.