Photoinduced large polaron transport and dynamics in organic–inorganic hybrid lead halide perovskite with terahertz probes

Abstract

Organic-inorganic hybrid metal halide perovskites (MHPs) have attracted tremendous attention for optoelectronic applications. The long photocarrier lifetime and moderate carrier mobility have been proposed as results of the large polaron formation in MHPs. However, it is challenging to measure the effective mass and carrier scattering parameters of the photogenerated large polarons in the ultrafast carrier recombination dynamics. Here, we show, in a one-step spectroscopic method, that the optical-pump and terahertz-electromagnetic probe (OPTP) technique allows us to access the nature of interplay of photoexcited unbound charge carriers and optical phonons in polycrystalline CH3NH3PbI3 (MAPbI3) of about 10 μm grain size. Firstly, we demonstrate a direct spectral evidence of the large polarons in polycrystalline MAPbI3. Using the Drude–Smith–Lorentz model along with the Frӧhlich-type electron-phonon (e-ph) coupling, we determine the effective mass and scattering parameters of photogenerated polaronic carriers. We discover that the resulting moderate polaronic carrier mobility is mainly influenced by the enhanced carrier scattering, rather than the polaron mass enhancement. While, the formation of large polarons in MAPbI3 polycrystalline grains results in a long charge carrier lifetime at room temperature. Our results provide crucial information about the photo-physics of MAPbI3 and are indispensable for optoelectronic device development with better performance.

Real-time observation of the buildup of polaron in α-FAPbI3

“…As shown in Fig. S 11b , transient optical conductivity acquired at 5 ps and 100 ps delay times after the photoexcitation also shows two resonance peaks at ~0.4 THz (P2) and ~1 THz (P1), indicating the relatively long transportation lifetime for the metastable polarons 29 , 38 . Therefore, the duration of the photo-current oscillation is corresponding to anharmonic coupling time between the Dember current and the lattice vibration, and hence could be connected with the polarons formation time.…”

“…S 4 , the thickness of 0.95FA and 0.85FA are ~658 nm and ~534 nm, respectively. The penetration depth of the pump pulse is taken to be about 1 μm 29 , 30 , which is larger than the thicknesses of the samples. Therefore, the dominant contribution to the observed terahertz pulse in our experiment is attributed to the photo-Dember current origin from the bulk effect.…”

High‐Quality 0D Cs4PbBr6‐Based Dense Wafer for High‐Sensitivity X‐Ray Detection and High‐Resolution Imaging in Harsh Environment

“…Generally, a large voltage bias is required during detection to promote carrier collection efficiency. [ 49 ] Still, notorious ion migration could also be accelerated at the same time, then causing severe baseline drift. [ 50 ] The key to settling the trade‐off is to increase the activation energy for ionic transport ( E a ), which is used to evaluate ion migration quantitatively (detailly illustrated in the Calculation Section in the Supporting Information).…”

Fabrication of anti-icing/de-icing surfaces by femtosecond laser

“…Femtosecond laser fabrication technologies have advantages in ultrashort pulse duration, ultra-high instantaneous power, ultra-fine processing structure ( You et al, 2020 ; Zheng et al, 2020 ; Fu et al, 2021 ; Zhang et al, 2021 ; Jin et al, 2022 ). In particular, the fine micro-/nano-structures play a vital role in the aspect controlling surface wettability, such as de-icing, anti-icing, superhydrophobic, superoleophobic, and slippery surface ( Yong et al, 2017 ; Yong J. et al, 2019 ; Feng and Yong, 2020 ; Yong et al, 2020 ; Yong et al, 2022a ).…”