期刊
JOURNAL OF PHYSICAL CHEMISTRY C
卷 122, 期 25, 页码 13399-13406出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpcc.7b11118
关键词
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资金
- Department of Science & Technology (Government of India)
- CeNS, Bengaluru
- Science and Engineering Board (SERB) [SR/S2/RJN-61/2012]
- DST Nanomission Thematic Unit [SR/NM/TP-13/2016]
- IISER Pune
- UGC
All-inorganic cesium lead halide (CsPbX3; X = Cl, Br, and I) perovskite nanocubes (NCs) exhibit fascinating optical and optoelectronic properties. Postsynthesis anion exchange by mixing NCs with reactive anion species has emerged as a unique strategy to control their composition and band gap. For example, we started with CsPbBr3 NCs with intense green emission, and then anion exchange with iodide ions yields CsPb(Br/I)(3) mixed halides and CsPbI3 with emission color systematically varying in the green-red region. However, the internal structure of the anion exchanged perovskite NCs is not probed. It is believed that the NCs possess a homogeneous alloyed composition, but X-ray diffraction pattern could not give evidence for such alloy formation, because the crystal structure also varies with anion composition. Here, we elucidate the internal heterostructure of anion-exchanged NCs using variable energy hard X-ray photoelectron spectroscopy. The results show that, in contrast to a homogeneous alloy, there is a significant inhomogeneity in the composition across the radius of NCs. The surface of CsPb(Br/I)(3) NCs is rich with exchanged iodide ions, whereas the core is rich with native bromide ions. Even CsPbI3 NCs obtained after assumed complete anion exchange show a small amount of bromide ions in the core. This finding of gradient internal heterostructure inside the anion-exchanged NCs will be important for future understanding of electronic properties and stability-related issues of CsPbX3 NCs.
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