Trapping effects and surface/interface recombination of carrier recombination in single- or poly-crystalline metal halide perovskites

Abstract

The lifetime of a carrier is a crucial parameter for solar cell materials, and metal halide perovskite materials are promising for solar cell applications. In this study, we observed carrier recombination using time-resolved photoluminescence (TR-PL) and microwave photoconductivity decay (μ-PCD) in metal halide perovskite materials: NH3CH3PbI3 (MAPbI3), NH3CH3PbBr3 (MAPbBr3), and CsPbBr3 with single- and poly-crystalline structures. By comparing the decay curves of TR-PL and μ-PCD, we found trap levels in the band gap for all the materials. We employed two excitation wavelengths for the μ-PCD measurements, and we observed faster μ-PCD signal decays for short wavelength excitation for MAPbBr3 and CsPbBr3. Additionally, we established that the poly-crystals exhibited faster decay compared with the single crystals for MAPbBr3 and CsPbBr3. Therefore, we concluded that there are significant contributions of the interface and surface recombination on carrier recombination for MAPbBr3 and CsPbBr3, but not for MAPbI3.

Unravelling material properties of halide perovskites by combined microwave photoconductivity and time-resolved photoluminescence spectroscopy

“…Consequently, it can be understood that for unequal excess charge carrier densities the trPL signal is most sensitive to the minority charge carrier type, while the microwave photoconductivity signal will follow the sum of charge carriers. 11,16,24 This situation typically occurs in the presence of charge selective traps. In this case, the trPL signal diminishes quickly because minority charge carriers are either trapped or rapidly recombine due to the high density of majority carriers.…”

“…10 Finally, Lobo et al performed comparative trPL and microwave photoconductivity measurements to investigate the presence of minority carrier traps in poly- and single-crystalline lead halide perovskites. 11…”

“…10 Finally, Lobo et al performed comparative trPL and microwave photoconductivity measurements to investigate the presence of minority carrier traps in poly-and single-crystalline lead halide perovskites. 11 Nonetheless, simple trPL measurements are still the most prevalently employed method to extract carrier lifetimes by a large majority of the research community, due to their contactless, reliable, fast, and non-destructive nature. Nevertheless, the extraction of material parameters from trPL measurements is not straightforward since the transients, especially for perovskites, are usually multi-exponential.…”

Surface recombination velocities for the (100) and (001) crystal faces of bismuth vanadate single crystals

“…Various methods have been used to observe the carrier lifetime in photocatalytic materials [22][23][24][25]. Transient absorption spectroscopy is a common method to characterize carrier lifetime in photocatalysts, however, it is sensitive only at high excited carrier densities due to relatively low absorption changes by excess free carriers [26,27].…”

“…Transient absorption spectroscopy is a common method to characterize carrier lifetime in photocatalysts, however, it is sensitive only at high excited carrier densities due to relatively low absorption changes by excess free carriers [26,27]. Time-resolved photoluminescence (TR-PL) and microwave photoconductivity decay (µ-PCD) are sensitive methods even at low excited carrier densities [25,[28][29][30][31][32]. In particular, µ-PCD is advantageous in sensitivity if the thickness and conductivity of the samples are low enough [18,20,33].…”