Abstract
We synthesize colloidal nanocrystals (NCs) of Rb3InCl6, composed of isolated metal halide octahedra (“0D”), and of Cs2NaInCl6 and Cs2KInCl6 double perovskites, where all octahedra share corners and are interconnected (“3D”), with the aim to elucidate and compare their optical features once doped with Sb3+ ions. Our optical and computational analyses evidence that the photoluminescence quantum yield (PLQY) of all these systems is consistently lower than that of the corresponding bulk materials due to the presence of deep surface traps from under-coordinated halide ions. Also, Sb-doped “0D” Rb3InCl6 NCs exhibit a higher PLQY than Sb-doped “3D” Cs2NaInCl6 and Cs2KInCl6 NCs, most likely because excitons responsible for the PL emission migrate to the surface faster in 3D NCs than in 0D NCs. We also observe that all these systems feature a large Stokes shift (varying from system to system), a feature that should be of interest for applications in photon management and scintillation technologies. Scintillation properties are evaluated via radioluminescence experiments, and re-absorption-free waveguiding performance in large-area plastic scintillators is assessed using Monte Carlo ray-tracing simulations.
Highlights
We synthesize colloidal nanocrystals (NCs) of Rb3InCl6, composed of isolated metal halide octahedra (“0D”), and of Cs2NaInCl6 and Cs2KInCl6 double perovskites, where all octahedra share corners and are interconnected (“3D”), with the aim to elucidate and compare their optical features once doped with Sb3+ ions
The broad family of double perovskites (DPs), having chemical formula A2B+B3+X6 and a crystal structure composed of BX6 corner-sharing octahedra surrounded by A+ cations (Scheme 1, left side), is promising and offers a fertile ground for new discoveries.[8−13] Various DP materials of the Cs2B+B3+Cl6 type have been investigated in a short time span,[9,14−21] and all of them were found to have a weak PL emission in both bulk and nanoscale dimensions, stemming from either an indirect bandgap or, in the case of direct bandgap materials, a parity-forbidden transition.[13,22−28]
Based on our computational analysis we suggest that, in the 0D case, the isolated [SbCl6] octahedra form self-trapped excitons (STEs) that are less likely to migrate to a defect-rich surface of the
Summary
Authors Dongxu Zhu − Nanochemistry Department, Istituto Italiano di Tecnologia, 16163 Genova, Italy Matteo L. Zaffalon − Dipartimento di Scienza dei Materiali, Università degli Studi di Milano Bicocca, 20125 Milano, Italy Juliette Zito − Nanochemistry Department, Istituto Italiano di Tecnologia, 16163 Genova, Italy; Dipartimento di Chimica e Chimica Industriale, Università degli Studi di Genova, 16146 Genova, Italy Francesca Cova − Dipartimento di Scienza dei Materiali, Università degli Studi di Milano Bicocca, 20125 Milano, Italy; orcid.org/0000-0001-7367-109X Francesco Meinardi − Dipartimento di Scienza dei Materiali, Università degli Studi di Milano Bicocca, 20125 Milano, Italy. Notes The authors declare no competing financial interest
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