Are Shockley-Read-Hall and ABC models valid for lead halide perovskites?

Abstract

Metal halide perovskites are an important class of emerging semiconductors. Their charge carrier dynamics is poorly understood due to limited knowledge of defect physics and charge carrier recombination mechanisms. Nevertheless, classical ABC and Shockley-Read-Hall (SRH) models are ubiquitously applied to perovskites without considering their validity. Herein, an advanced technique mapping photoluminescence quantum yield (PLQY) as a function of both the excitation pulse energy and repetition frequency is developed and employed to examine the validity of these models. While ABC and SRH fail to explain the charge dynamics in a broad range of conditions, the addition of Auger recombination and trapping to the SRH model enables a quantitative fitting of PLQY maps and low-power PL decay kinetics, and extracting trap concentrations and efficacies. However, PL kinetics at high power are too fast and cannot be explained. The proposed PLQY mapping technique is ideal for a comprehensive testing of theories and applicable to any semiconductor.

Charge transfer rates and electron trapping at buried interfaces of perovskite solar cells

“…23 However, in most cases, quenching of PL signals by charge separation, such as charge transfer at chargeselective contacts, and by increased recombination rates cannot be unambiguously distinguished, and quite strong dependencies of PL transients on experimental conditions can make the analysis of PL transients even more complicated. [24][25][26][27] In contrast to J-V and PL measurements, SPV measurements track the change in the surface potential upon photoexcitation and give information about the direction of charge separation, i.e., a positive (negative) SPV signal suggests the preferred separation of holes (electrons) toward the sample's surface. 17 For OSCs, intensitymodulated SPV microscopy has been shown to be a valuable tool to probe variations in carrier dynamics due to heterogeneity in the buried surface chemistry.…”

Apparent Defect Densities in Halide Perovskite Thin Films and Single Crystals

“…What is possible, however, is to measure the impact of traps on recombination via the lifetime of charge carriers. , Eventually, the lifetime or the recombination coefficients will control the open-circuit voltage of a device . The actual defect density may not be such a good figure of merit in the first place if we consider how large variations of capture coefficients can be.…”

Enhanced Photoluminescence of Halide Perovskite Nanocrystals Mediated by a Higher-Order Topological Metasurface

“…To describe the optical relaxation of free carriers in the perovskite layer, we apply the so-called “ABC model” rate equation where N fc is the photoexcited free carrier concentration and A is monomolecular (nonradiative), B is bimolecular (radiative), and C is trimolecular (Auger) recombination constants. We convert this expression to the following form where N 0 is the initial generated carrier concentration and is the normalized PL intensity. Using this equation with a neglected Auger recombination term ( C = 0) and the experimental data from Figure a, we obtain the monomolecular and bimolecular recombination constants from the fit of the curves in Figure b (see the values in Table ).…”