Pramanik Avijit, Sinha Sudarson Sekhar, Gates Kaelin, Nie Jing, Han Fengxiang X, Ray Paresh Chandra
Department of Chemistry and Biochemistry, Jackson State University, Jackson, Mississippi 39217, United States.
ACS Omega. 2023 Mar 31;8(14):13202-13212. doi: 10.1021/acsomega.3c00477. eCollection 2023 Apr 11.
Despite black cubic phase α-CsPbI nanocrystals having an ideal bandgap of 1.73 eV for optoelectronic applications, the phase transition from α-CsPbI to non-perovskite yellow δ-CsPbI phase at room temperature remains a major obstacle for commercial applications. Since γ-CsPbI is thermodynamically stable with a bandgap of 1.75 eV, which has great potential for photovoltaic applications, herein we report a conceptually new method for the targeted design of phase stable and near unity photoluminescence quantum yield (PLQY) two-dimensional (2D) γ-CsPbI nanoplatelets (NPLs) and one-dimensional (1D) γ-CsPbI nanobelts (NBs) by wavelength dependent light-induced assembly of CsPbI cubic nanocrystals. This article demonstrates for the first time that by varying the excitation wavelengths, one can design air stable desired 2D nanoplatelets or 1D nanobelts selectively. Our experimental finding indicates that 532 nm green light-driven self-assembly produces phase stable and highly luminescent γ-CsPbI NBs from CsPbI nanocrystals. Moreover, we show that a 670 nm red light-driven self-assembly process produces stable and near unity PLQY γ-CsPbI NPLs. Systematic time-dependent microscopy and spectroscopy studies on the morphological evolution indicates that the electromagnetic field of light triggered the desorption of surface ligands from the nanocrystal surface and transformation of crystallographic phase from α to γ. Detached ligands played an important role in determining the morphologies of final structures of NBs and NPLs from nanocrystals via oriented attachment along the [110] direction initially and then the [001] direction. In addition, XRD and fluorescence imaging data indicates that both NBs and NPLs exhibit phase stability for more than 60 days in ambient conditions, whereas the cubic phase α-CsPbI nanocrystals are not stable for even 3 days. The reported light driven synthesis provides a simple and versatile approach to obtain phase pure CsPbI for possible optoelectronic applications.
尽管黑色立方相α-CsPbI纳米晶体对于光电子应用具有1.73 eV的理想带隙，但在室温下从α-CsPbI到非钙钛矿黄色δ-CsPbI相的相变仍然是商业应用的主要障碍。由于γ-CsPbI具有1.75 eV的带隙且热力学稳定，在光伏应用方面具有巨大潜力，因此我们在此报告一种概念上全新的方法，通过基于波长依赖的光诱导CsPbI立方纳米晶体组装，有针对性地设计相稳定且光致发光量子产率（PLQY）接近单位值的二维（2D）γ-CsPbI纳米片（NPL）和一维（1D）γ-CsPbI纳米带（NB）。本文首次证明，通过改变激发波长，可以选择性地设计出对空气稳定的所需2D纳米片或1D纳米带。我们的实验发现表明，532 nm绿光驱动的自组装过程能从CsPbI纳米晶体中产生相稳定且高发光的γ-CsPbI NB。此外，我们还表明，670 nm红光驱动的自组装过程能产生稳定且PLQY接近单位值的γ-CsPbI NPL。对形态演变进行的系统的时间分辨显微镜和光谱研究表明，光的电磁场触发了纳米晶体表面配体的解吸以及晶体相从α到γ的转变。脱离的配体在通过最初沿[110]方向、然后沿[001]方向的定向附着来确定纳米晶体最终结构（NB和NPL）的形态方面发挥了重要作用。此外，XRD和荧光成像数据表明，NB和NPL在环境条件下60多天内都表现出相稳定性，而立方相α-CsPbI纳米晶体甚至3天就不稳定了。所报道的光驱动合成方法为获得用于可能的光电子应用的相纯CsPbI提供了一种简单且通用的途径。
