Publication date: 28th August 2024
Lead halide perovskite nanocrystals (NCs) have emerged recently inspired by the surge of the efficiencies of the solar cells based on thin film perovskites. Two critical problems hindering their widespread application are yet to be resolved: (i) high toxicity due to the presence of heavy metal lead, (ii) relative instability on the presence of various environmental factors. To address these problems, recently, significant efforts to develop lead-free colloidal NCs have been made.[1] Some of the most promising alternative, less toxic, and more stable materials are bismuth halide perovskites (BiHPs), A3Bi2X9. However, there is still a lot of confusion around the synthesis and properties of BiHP NCs for several fundamental and practical reasons: variety of possible structures, potential luminescent impurities, questionable presence of the quantum confinement in such 0D materials, and rare reliable synthetic reports on small BiHP NCs.
In our work, we try to address the above problems using two approaches. First, we have developed rational design to synthesize small and monodisperse colloidal BiHP NCs in a reproducible manner. We study the hot injection synthesis, which allowed obtaining <10 nm-sized NCs by optimizing halide precursors. Then, we will focus on the original method of templated synthesis of BiHP NCs first synthesizing small cesium halide NCs and then converting them by cation insertion into Cs3Bi2X9 NCs with low size dispersion (manuscript in preparation).
In the second part, we will discuss a powerful method for studying the fundamental properties of BiHPs and other Pb-free perovskites by encapsulating them into the mesoporous silica with ordered pores of 2-9 nm.[2] This offers an appropriate means to control the size of the NCs precisely, access small sizes in the quantum confinement regime, and systematically study the effect of size on their properties. The fitted optical absorption spectra revealed that the bandgap of BiHP NCs scale with the pore size. In addition, their exciton binding energies were calculated to be 70-400 meV. It is unambiguously demonstrated for the first time that the 0D BiHPs exhibit the quantum confinement effect. This conclusion is strongly supported by DFT calculations on BiHP clusters with varying dimensions.
MITI interdisciplinary program and from the French National Research Agency (grant ANR EncaPer ANR-23-CE09-0013-01)
R.S. Lamba, A. S. Vasenko, S. Pouget, S. Schlutig, M. Vidal, B. Lebeau, W. L. Ling, V. Artero, C. Rivaux
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