Free Carrier, Exciton, and Phonon Dynamics in Lead‐Halide Perovskites Studied with Ultrafast Terahertz Spectroscopy

Abstract

Terahertz time‐domain spectroscopy is a noncontact, coherent technique that can probe dynamics of carriers, phonons and excitons, and the interplay among these degrees of freedom, which determines the functionalities of the system. In the past few years, lead‐halide perovskites have shown to be a promising class of materials in the areas of solar cells, light emitting diodes, lasers, photodetectors, and field‐effect transistors. In these electronic and photonic devices, the knowledge of the dynamics of charge carriers and other low‐energy excitations is crucial to understand the underlying physics that ultimately determines the device performances. Here, some of the most representative works in the area of halide perovskite research using terahertz time‐domain spectroscopy and time‐resolved terahertz spectroscopy are reviewed, highlighting the power of ultrafast terahertz techniques on this class of material system.

Terahertz Conductivity Analysis for Highly Doped Thin-Film Semiconductors

“…an expression which is commonly used to calculate the photoconductivity of thin films from THz transmission measurements [6,7,9,10,[31][32][33]. Figure 4 shows the deviation of the real part of the photoconductivity value calculated using Eq.…”

“…In this section, we discuss a simple experimental technique of estimating the apparent dark conductivity, necessary to calculate the time resolved photoconductivity of doped thin films in a optical-pump-THz-probe study. As discussed by Zhao and Chia [33], OPTP measurement is a 1D THz-TDS scan, in which the magnitude of a single-cycle THz pulse is measured at its peak for different pump-probe time delays. The measurement provides a frequency-averaged, time-dependent real part of the photoconductivity [33] of the sample.…”

“…As discussed by Zhao and Chia [33], OPTP measurement is a 1D THz-TDS scan, in which the magnitude of a single-cycle THz pulse is measured at its peak for different pump-probe time delays. The measurement provides a frequency-averaged, time-dependent real part of the photoconductivity [33] of the sample.…”

Materials for Terahertz Optical Science and Technology

“…Over the years, a considerable part of terahertz research has been focused on development of broadband and strong-THz emission using laser-driven material systems that have enabled emerging applications in the nonlinear THz spectroscopy. The works discussed by P. Kuzel et al [3] and D. Zhao et al [4] reveal that in bulk-bandgap semiconductors such as low-dimensional nanocrystals and perovskites, the major contribution to their carrier dynamics and charge transport properties is through change in free carrier density in the material during the interband transition using near-infrared pulses, which also reveals the positive change in THz photoconductivity. A. Fülöp et al [2] ).…”

“…On the other hand, investigating the properties of THz emissivity enables noninvasive and ultrafast probing of the underlying exotic physical processes in the complex correlated systems such as high-temperature superconductors and several other transition metal oxides (TMOs), as reported by D. S. Rana excitations. The works discussed by P. Kuzel et al [3] and D. Zhao et al [4] reveal that in bulk-bandgap semiconductors such as low-dimensional nanocrystals and perovskites, the major contribution to their carrier dynamics and charge transport properties is through change in free carrier density in the material during the interband transition using near-infrared pulses, which also reveals the positive change in THz photoconductivity. On the other hand, in Dirac materials such as graphene and topological insulators, the carrier dynamics are strongly influenced by the interplay between the photoinduced change in Drude weight and carrier scattering rate (see the review works by C. In and H. Choi [5] ).…”