Centre for Nano Science and Technology (CNST@PoliMi), Istituto Italiano di Tecnologia, Via Pascoli 70, Milan 20133, Italy.
Molecular Materials and Nanosystems & Institute for Complex Molecular Systems, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands.
Nanoscale. 2023 Mar 23;15(12):5712-5719. doi: 10.1039/d2nr06345j.
Metal halide perovskite nanocrystals (NCs) are promising for photovoltaic and light-emitting applications. Due to the softness of their crystal lattice, structural modifications have a critical impact on their optoelectronic properties. Here we investigate the size-dependent optoelectronic properties of CsPbI NCs ranging from 7 to 17 nm, employing temperature and pressure as thermodynamic variables to modulate the energetics of the system and selectively tune the interatomic distances. By temperature-dependent photoluminescence spectroscopy, we have found that luminescence quenching channels exhibit increased non-radiative losses and weaker exciton-phonon coupling in bigger particles, in turn affecting the luminescence efficiency. Through pressure-dependent measurements up to 2.5 GPa, supported by XRD characterization, we revealed a NC-size dependent solid-solid phase transition from the γ-phase to the δ-phase. Importantly, the optical response to these structural changes strongly depends on the size of the NC. Our findings provide an interesting guideline to correlate the size and structural and optoelectronic properties of CsPbI NCs, important for engineering the functionalities of this class of soft semiconductors.
金属卤化物钙钛矿纳米晶体（NCs）在光电和发光应用方面具有广阔的前景。由于其晶格的柔软性，结构的修改对其光电性能有至关重要的影响。在这里，我们研究了从 7nm 到 17nm 尺寸的 CsPbI NCs 的尺寸依赖性光电性质，采用温度和压力作为热力学变量来调节系统的能量状态，并选择性地调整原子间距离。通过温度相关的光致发光光谱，我们发现，在较大的颗粒中，发光猝灭通道表现出增加的非辐射损耗和较弱的激子-声子耦合，这反过来又影响了发光效率。通过高达 2.5GPa 的压力相关测量，结合 XRD 特性，我们揭示了从 γ 相到 δ 相的 NC 尺寸相关的固-固相变。重要的是，对这些结构变化的光学响应强烈依赖于 NC 的尺寸。我们的研究结果为 CsPbI NCs 的尺寸、结构和光电性质之间的相关性提供了一个有趣的指导，这对于设计这类软半导体的功能非常重要。
