Homogeneous Optical Line Widths in Hybrid Ruddlesden-Popper Metal Halides Can Only Be Measured Using Nonlinear Spectroscopy
Homogeneous Optical Line Widths in Hybrid Ruddlesden-Popper Metal Halides Can Only Be Measured Using Nonlinear Spectroscopy
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DOI：
10.1021/acs.jpcc.2c00658
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发表时间：
2022-03-31
影响因子：
3.7
通讯作者：
Silva-Acuna, Carlos
中科院分区：
文献类型：
--
作者：
Kandada, Ajay Ram Srimath;Li, Hao;Silva-Acuna, Carlos
半导体中的均匀光致发光光谱线宽携带了大量有关初级光激发与其动态环境以及多粒子之间耦合的信息。在不均匀展宽占总光线宽度的限制下，可以通过温度相关的稳态光致发光光谱来严格区分不均匀和均匀的贡献。这是可能的，因为唯一与温度相关的现象是光学移相，它定义了均匀线宽，因为该过程是通过声子散射来介导的。然而，如果均匀和非均匀线宽相当，如混合拉德尔斯登-波普尔金属卤化物的情况，线性光谱测量的温度依赖性无法严格区分均匀和非均匀对总线宽的贡献，因为线形状不包含可以通过改变温度来隔离的纯洛伦兹分量。此外，如果由扩散限制过程驱动，特别是如果通过光致发光测量，则对稳态光致发光线形状的不均匀贡献不一定与温度无关。另一方面，非线性相干光学光谱确实允许在所有不均匀区域中分离均匀和不均匀谱线展宽贡献。因此，这些提供了对多体相互作用本质的见解，而这是依赖温度的线性光谱完全无法获得的。当应用于 Ruddlesden-Popper 金属卤化物时，这些技术确实使我们能够定量评估激子-声子和激子-激子散射机制。在这里，我们将讨论如何在激子极化子框架内有效合理化 Ruddlesden-Popper 金属卤化物的相干线形状。
The homogeneous photoluminescence spectral linewidth in semiconductors carries a wealth of information on the coupling of primary photo excitations with their dynamic environment as well as between multiparticles. In the limit in whichinhomogeneous broadening dominates the total optical line widths, the inhomogeneous and homogeneous contributions can berigorously separated by temperature-dependent steady-state photo-luminescence spectroscopy. This is possible because the onlytemperature-dependent phenomenon is optical dephasing, whichdefines the homogeneous line width, since this process is mediatedby scattering with phonons. However, if the homogeneous andinhomogeneous line widths are comparable, as is the case in hybridRuddlesden-Popper metal halides, the temperature dependence oflinear spectral measurementcannotseparate rigorously thehomogeneous and inhomogeneous contributions to the total line width because the line shape doesnotcontain purely Lorentziancomponents that can be isolated by varying the temperature. Furthermore, the inhomogeneous contribution to the steady-statephotoluminescence line shape is not necessarily temperature independent if driven by diffusion-limited processes, particularly ifmeasured by photoluminescence. Nonlinear coherent optical spectroscopies, on the other hand, do permit separation ofhomogeneous and inhomogeneous line broadening contributions in all regimes of inhomogeneity. Consequently, these offer insights into the nature of many-body interactions that are entirely inaccessible to temperature-dependent linear spectroscopies. When applied to Ruddlesden-Popper metal halides, these techniques have indeed enabled us to quantitatively assess the exciton-phonon and exciton-exciton scattering mechanisms. Here, we will discuss our perspective on how the coherent line shapes of Ruddlesden-Popper metal halides can be effectively rationalized within an exciton polaron framework.