Hazra Vishwadeepa, Mondal Sudipta, Pattanayak Pradip, Bhattacharyya Sayan
Department of Chemical Sciences, and Centre for Advanced Functional Materials, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur, 741246, India.
Small. 2024 Feb;20(8):e2304920. doi: 10.1002/smll.202304920. Epub 2023 Oct 10.
The transition from 3D to 2D lead halide perovskites is traditionally led by the lattice incorporation of bulky organic cations. However, the transformation into a coveted 2D superlattice-like structure by cationic substitution at the Pb site of 3D perovskite is unfamiliar. It is demonstrated that the gradual increment of [Sn ] alters the FASn Pb I nanocrystals into the Ruddlesden-Popper-like nanoplatelets (NPLs), with surface-absorbed oleic acid (OA) and oleylamine (OAm) spacer ligand at 80 °C (FA : formamidinium cation). These NPLs are stacked either by a perfect alignment to form the superlattice or by offsetting the NPL edges because of their lateral displacements. The phase transition occurs from the Sn/Pb ratio ≥0.011, with 0.64 wt% of Sn species. At and above Sn/Pb = 0.022, the NPL superlattice stacks start to grow along [00l] with a repeating length of 4.37(3) nm, comprising the organic bilayer and the inorganic block having two octahedral layers (n = 2). Besides, a photoluminescence quantum yield of 98.4% is obtained with Sn/Pb = 0.011 (n ≥ 4), after surface passivation by trioctylphosphine (TOP).
从三维到二维的卤化铅钙钛矿的转变传统上是由大体积有机阳离子的晶格掺入导致的。然而，通过在三维钙钛矿的铅位点进行阳离子取代而转变为令人垂涎的二维超晶格状结构却并不常见。研究表明，[Sn]的逐渐增加会在80°C下（FA：甲脒阳离子）将FASnPbI纳米晶体转变为类Ruddlesden-Popper纳米片（NPLs），其表面吸附有油酸（OA）和油胺（OAm）间隔配体。这些NPLs要么通过完美对齐堆叠形成超晶格，要么由于其横向位移而使NPL边缘错开堆叠。当Sn/Pb比≥0.011且Sn物种含量为0.64 wt%时发生相变。当Sn/Pb = 0.022及以上时，NPL超晶格堆叠开始沿[00l]方向生长，重复长度为4.37(3) nm，由有机双层和具有两个八面体层（n = 2）的无机块组成。此外，在用三辛基膦（TOP）进行表面钝化后，Sn/Pb = 0.011（n≥4）时的光致发光量子产率达到98.4%。
