Okamoto Takuya, Biju Vasudevanpillai
Research Institute for Electronic Science, Hokkaido University, Sapporo, Hokkaido, 001-0020, Japan.
Graduate School of Environmental Science, Hokkaido University, Sapporo, Hokkaido, 060-0810, Japan.
Small. 2023 Aug;19(32):e2303496. doi: 10.1002/smll.202303496. Epub 2023 May 12.
Supramolecularly assembled high-order supercrystals (SCs) help control the dielectric, electronic, and excitonic properties of semiconductor nanocrystals (NCs) and quantum dots (QDs). Ligand-engineered perovskite NCs (PNCs) assemble into SCs showing shorter excitonic lifetimes than strongly dielectric PNC films showing long photoluminescence (PL) lifetimes and long-range carrier diffusion. Monodentate to bidentate ligand exchange on ≈ 8 nm halide perovskite (APbX ; A:Cs/MA, X:Br/I) PNCs generates mechanically stable SCs with close-packed lattices, overlapping electronic wave functions, and higher dielectric constant, providing distinct excitonic properties from single PNCs or PNC films. From Fast Fourier Transform (FFT) images, time-resolved PL, and small-angle X-ray scattering, structurally and excitonically ordered large SCs are identified. An Sc shows a smaller spectral shift (<35 meV) than a PNC film (>100 meV), a microcrystal (>100 meV), or a bulk crystal (>100 meV). Also, the exciton lifetime (<10 ns) of an SC is excitation power-independent in the single exciton regime 〈N〉<1, comparable to an isolated PNC. Therefore, bidentate-ligand-assisted SCs help overcome delayed exciton or carrier recombination in halide perovskite nanocrystal assemblies or films.
超分子组装的高阶超晶体（SCs）有助于控制半导体纳米晶体（NCs）和量子点（QDs）的介电、电子和激子特性。配体工程化的钙钛矿纳米晶体（PNCs）组装成SCs，其激子寿命比具有长光致发光（PL）寿命和长程载流子扩散的强介电PNC薄膜短。在约8纳米卤化物钙钛矿（APbX ；A:Cs/MA，X:Br/I）PNCs上进行单齿到双齿配体交换，可生成具有紧密堆积晶格、重叠电子波函数和更高介电常数的机械稳定SCs，提供与单个PNC或PNC薄膜不同的激子特性。通过快速傅里叶变换（FFT）图像、时间分辨PL和小角X射线散射，确定了结构和激子有序的大SCs。与PNC薄膜（>100 meV）、微晶（>100 meV）或块状晶体（>100 meV）相比，SCs显示出更小的光谱位移（<35 meV）。此外，在单激子区域〈N〉<1时，SCs的激子寿命（<10 ns）与激发功率无关，与孤立的PNC相当。因此，双齿配体辅助的SCs有助于克服卤化物钙钛矿纳米晶体组件或薄膜中的延迟激子或载流子复合。
