Abstract
We devised a hot-injection synthesis to prepare colloidal double-perovskite Cs2NaBiCl6 nanocrystals (NCs). We also examined the effects of replacing Na+ with Ag+ cations by preparing and characterizing Cs2Na1–xAgxBiCl6 alloy NCs with x ranging from 0 to 1. Whereas Cs2NaBiCl6 NCs were not emissive, Cs2Na1–xAgxBiCl6 NCs featured a broad photoluminescence band at ∼690 nm, Stokes-shifted from the respective absorption by ≥1.5 eV. The emission efficiency was maximized for low Ag+ amounts, reaching ∼3% for the Cs2Na0.95Ag0.05BiCl6 composition. Density functional theory calculations coupled with spectroscopic investigations revealed that Cs2Na1–xAgxBiCl6 NCs are characterized by a complex photophysics stemming from the interplay of (i) radiative recombination via trapped excitons localized in spatially connected AgCl6–BiCl6 octahedra; (ii) surface traps, located on undercoordinated surface Bi centers, behaving as phonon-assisted nonradiative decay channels; and (iii) a thermal equilibrium between trapping and detrapping processes. These results offer insights into developing double-perovskite NCs with enhanced optoelectronic efficiency.
Highlights
We devised a hot-injection synthesis to prepare colloidal double-perovskite Cs2NaBiCl6 nanocrystals (NCs)
Nanocrystals (NCs) of lead halide perovskites have attracted significant interest in recent years and are promising candidate materials for various optoelectronic applications.[1−7] given the intrinsic toxicity of lead, which constrains the use of such materials in commercial devices, the scientific community is seeking for alternative stable lead-free metal halide perovskite compounds with comparable optical properties.[8,9]
The most promising candidates in this context are the so-called double perovskites (DPs), termed elpasolites, having the general formula A2B+B3+X6, characterized by a 3D perovskite structure made of aAl+terinoantsinogc[cBup+Xyi6n]ganthde[Bvo3+idXs6]incobrneetwr-eshenar.8in−g11ocTthaheeddriffaewreintht combinations of possible A+, B+, and B3+ ions create a richness of structures, making the elpasolites family interesting from a chemistry and a materials science point of view,[10] as well as for technological applications in photovoltaics,[12−14] artificial lighting, and photon management.[15]
Summary
Sergio Brovelli − Dipartimento di Scienza dei Materiali, Universitá degli Studi di Milano-Bicocca, 20125 Milano, Italy; orcid.org/0000-0002-5993-855X; Email: sergio.brovelli@ unimib.it. Valerio Pinchetti − Dipartimento di Scienza dei Materiali, Universitá degli Studi di Milano-Bicocca, 20125 Milano, Italy; orcid.org/0000-0003-3792-3661. Zhiya Dang − Nanochemistry Department, Istituto Italiano di Tecnologia, 16163 Genova, Italy. Andrea Olivati − Dipartimento di Scienza dei Materiali, Universitá degli Studi di Milano-Bicocca, 20125 Milano, Italy. Aiwei Tang − Department of Chemistry, School of Science, Beijing JiaoTong University, Beijing 100044, China; orcid.org/0000-0002-0716-0387. Zaffalon − Dipartimento di Scienza dei Materiali, Universitá degli Studi di Milano-Bicocca, 20125 Milano, Italy. Francesco Meinardi − Dipartimento di Scienza dei Materiali, Universitá degli Studi di Milano-Bicocca, 20125 Milano, Italy. Author Contributions ∇D.Z., J.Z., and V.P. contributed to this work
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