Fast non-ambipolar diffusion of charge carriers and the impact of traps and hot carriers on it in CsMAFA perovskite and GaAs

Abstract

We performed a comprehensive study of the charge carrier diffusion in the CsMAFA perovskite, one of the state-of-the-art perovskites for photovoltaic applications, starting from the diffusion of hot carriers to...

Transient Absorption Spectroscopy of Films: Impact of Refractive Index

“…To simplify modeling we assume that the total number of carriers stays the same. The carrier distribution change with time across the sample can be obtained by solving a one-dimensional diffusion equation. − The results of modeling for d = 500 nm film with diffusion coefficient D = 2 cm 2 s –1 is presented in Figure a. Here we assume the film optical density at the excitation wavelength to be 2, which is roughly the film absorbance at 600 nm.…”

“…The signal at 550 nm was normalized to match the 480 nm signal at late delay times. Reprinted with permission from ref ( 58 ). Copyright (2021) Royal Society of Chemistry.…”

Charge Transfer Kinetics in Halide Perovskites: On the Constraints of Time-Resolved Spectroscopy Measurements

“…The control of the film thickness and sample geometry becomes important if one is interested in probing the CTL/perovskite interface. Cross-comparison of these measurements for perovskite samples without CTLs can be used to (i) reveal the effect of surface trap states or (ii) determine the perpendicular charge carrier mobility of perovskite thin films. , However, care must be exercised, as the microstructure of the perovskite films (light scattering) can distort the TA signal and contain contribution from specular reflectance . TR can also be used in the case of nontransparent samples, where the probe light cannot pass through the sample and inhibit TA measurements (operating in transmission geometry).…”

Effect of Single-Crystal TiO2/Perovskite Band Alignment on the Kinetics of Electron Extraction

“…For example, the applied laser excitation intensity has an impact on both charge recombination and charge transfer processes at the TiO 2 /perovskite interface. , A potential barrier is shown to form at the TiO 2 /perovskite interface, which leads to charge accumulation, hindering electron transfer . The kinetics of the charge recombination and extraction processes can also be influenced by the perovskite film quality, such as grain size, , quantity of impurity phases, , and interface and surface defect densities. , In the case of front-side excitation (from the perovskite/air interface), the carrier diffusion process also needs to be taken into consideration before these carriers can be extracted by the ETL. − It is challenging to ensure the similarity of these parameters and present a meaningful comparison of charge carrier dynamics (and carrier extraction) in perovskites and at related interfaces. When using single-crystal ETLs, at least variation arising from the structure and surface area of the ETLs can be mitigated.…”

“… 38 , 39 In the case of front-side excitation (from the perovskite/air interface), the carrier diffusion process also needs to be taken into consideration before these carriers can be extracted by the ETL. 40 − 42 It is challenging to ensure the similarity of these parameters and present a meaningful comparison of charge carrier dynamics (and carrier extraction) in perovskites and at related interfaces. When using single-crystal ETLs, at least variation arising from the structure and surface area of the ETLs can be mitigated.…”