Photocurrent Spectroscopy of Perovskite Layers and Solar Cells: A Sensitive Probe of Material Degradation

Holovský, Jakub; Wolf, Stefaan De; Werner, Jérémie; Remeš, Z.; Müller, Martin; Neyková, Neda; Ledinský, Martin; Cerna, Ladislava; Hrzina, Pavel; Löper, P.; Niesen, Bjoern; Ballif, Christophe

doi:10.1021/acs.jpclett.6b02854

Cited by 20 publications

(16 citation statements)

References 45 publications

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“…FTPS, on the other hand, is sensitive only to the absorption contributing to photocurrent and may, therefore, be sensitive to deep defects in the main photoactive phase (CH 3 NH 3 PbI 3 ). Moreover, in agreement with our previous report, 40 we assume that both electrons and holes have to be collected, and because of the short lifetime of electron−hole pairs inside of the PbI 2 phase, this effectively suppresses any possible photogeneration inside of the PbI 2 phase. This can already be seen from the comparison of FTPS spectra of the fresh samples scaled at their maximum in the upper panel of Figure 7.…”

supporting

confidence: 91%

“…The parasitic absorption of a thin layer of unreacted PbI 2 that does not contribute to photocurrent is indicated by the yellow area. However, interestingly, thanks to charge transfer between PbI 2 and CH 3 NH 3 PbI 3 , this layer does not hinder carrier extraction from the CH 3 NH 3 PbI 3 phase. Figure shows that also in the case of the two-step sample at least 80% of blue LED light (2.64 eV) reaches the CH 3 NH 3 PbI 3 phase, so that both two-step and single-step cases are comparable.…”

mentioning

confidence: 98%

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Lead Halide Residue as a Source of Light-Induced Reversible Defects in Hybrid Perovskite Layers and Solar Cells

et al. 2019

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Advanced characterization methods avoiding transient effects in combination with solar cell performance monitoring reveal details of reversible light-induced perovskite degradation under vacuum. A clear signature of related deep defects in at least the 1 ppm range is observed by low absorptance photocurrent spectroscopy. An efficiency drop, together with deep defects, appears after minutes-long blue illumination and disappears after 1 h or more in the dark. Systematic comparison of perovskite materials prepared by different methods indicates that this behavior is caused by the lead halide residual phase inherently present in material prepared by the two-step method. X-ray photoelectron spectroscopy confirms that lead halide when illuminated decomposes into metallic lead and mobile iodine, which diffuses into the perovskite phase, likely producing interstitial defects. Single-step preparation, as well as preventing lead halide illumination, eliminates this effect.

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confidence: 91%

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confidence: 98%

Lead Halide Residue as a Source of Light-Induced Reversible Defects in Hybrid Perovskite Layers and Solar Cells

et al. 2019

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“…The slope of this linear behavior gives a direct access to the product αk 2 . The absorption coefficient can be measured via other methods such as Fourier transform photocurrent spectroscopy [42,43] or ellipsometry [44]. Therefore, one can extract a direct measurement of the external radiative recombination rate k 2 .…”

Section: A the Drift-diffusion Modelmentioning

confidence: 99%

Mapping Transport Properties of Halide Perovskites via Short-Time-Dynamics Scaling Laws and Subnanosecond-Time-Resolution Imaging

et al. 2021

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The excellent optoelectronic and transport properties of halide perovskites led to a rapid development of perovskite based optoelectronic devices. The fundamental understanding of charge carrier dynamics as well as the implementation of physical models able to accurately describe their behaviour are essential for further improvements in the field. Here, combining advanced modeling and characterization, a method for analyzing the short time dynamics of time resolved fluorescence imaging (TR-FLIM) decays is demonstrated. A theoretical scaling law for the time derivative of transient photoluminescence decays as a function of the excitation power is extracted. This scaling law, computed from classical drift-diffusion equations, defines an innovative and simple way to extract quantitative values for several transport parameters including the external radiative recombination coefficient. The model was notably applied on a set of images acquired with a temporal shift of 250 ps to map the top surface recombination velocity of a triple cation mixed halide perovskite thin film at the microscale. The development of high-time-resolution imaging techniques coupled with the scaling method for analyzing short-time dynamics provides a solid platform for the investigation of local heterogeneities in semiconductor materials and the accurate determination of the main parameters governing their carrier transport. I. INTRODUCTIONOver the last decade, lead-halide perovskites solar cells have proved to be a serious candidate for reaching large scale photovoltaic (PV) solar energy conversion, a much-needed solution to meet climate targets and move towards a low-carbon economy. However, despite this emerging technology has recently reached a record power conversion efficiency of 25.5% for a single junction device [1,2], several open questions persist in the scientific community, ranging from the nature and densities of the defects in the absorbers [3-5], the optimal design for the interfaces energetics in a full device [6,7], and the long term stability [7][8][9].The optimization of device performances goes along with the complete understanding of complex recombination processes occurring both in the bulk and at the interfaces. Due to the interplay of several chemical and physical parameters in these hybrid compounds, such

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“…Sub-bandgap absorptance spectroscopy is a relatively simple defect quantification method, which is well established in the material science of thin-film photovoltaic (PV) materials, such as microcrystalline silicon [1], hydrogenated amorphous silicon (a-Si:H) [2], organic semiconductors [3] and also recently hybrid perovskite materials [4][5][6][7]. Whereas other methods, such as conductivity or photoluminescence, are difficult to interpret and may give results affected by transient effects, sub-bandgap absorptance photoluminescence, are difficult to interpret and may give results affected by transient effects, subbandgap absorptance spectroscopy can already provide a relatively universal indication of semiconductor quality by looking at the sub-bandgap absorptance and the steepness of the absorption edge.…”

Section: Introductionmentioning

confidence: 99%

“…The advantage of FTPS compared to PDS is the ability to measure the defect density of absorber layers in complete solar cells. In hybrid perovskites, the main difference might be the lead iodide phase that exhibits differently [4,6,7], while in the case of a-Si:H the main difference is the sensitivity to the surface defects, that is higher in PDS, but can also distort FTPS spectra (see Figure 1a). Surface defect absorption may lead to erroneous features on the apparent (as evaluated) absorption coefficient.…”

Section: Introductionmentioning

confidence: 99%

Towards Quantitative Interpretation of Fourier-Transform Photocurrent Spectroscopy on Thin-Film Solar Cells

et al. 2020

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The method of detecting deep defects in photovoltaic materials by Fourier-Transform Photocurrent Spectroscopy has gone through continuous development during the last two decades. Still, giving quantitative predictions of photovoltaic device performance is a challenging task. As new materials appear, a prediction of potentially achievable open-circuit voltage with respect to bandgap is highly desirable. From thermodynamics, a prediction can be made based on the radiative limit, neglecting non-radiative recombination and carrier transport effects. Beyond this, more accurate analysis has to be done. First, the absolute defect density has to be calculated, taking into account optical effects, such as absorption enhancement, due to scattering. Secondly, the electrical effect of thickness variation has to be addressed. We analyzed a series of state-of-the-art hydrogenated amorphous silicon solar cells of different thicknesses at different states of light soaking degradation. Based on a combination of empirical results with optical, electrical and thermodynamic simulations, we provide a predictive model of the open-circuit voltage of a device with a given defect density and absorber thickness. We observed that, rather than the defect density or thickness alone, it is their product or the total number of defects, that matters. Alternatively, including defect absorption into the thermodynamic radiative limit gives close upper bounds to the open-circuit voltage with the advantage of a much easier evaluation.

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Photocurrent Spectroscopy of Perovskite Layers and Solar Cells: A Sensitive Probe of Material Degradation

Cited by 20 publications

References 45 publications

Lead Halide Residue as a Source of Light-Induced Reversible Defects in Hybrid Perovskite Layers and Solar Cells

Lead Halide Residue as a Source of Light-Induced Reversible Defects in Hybrid Perovskite Layers and Solar Cells

Mapping Transport Properties of Halide Perovskites via Short-Time-Dynamics Scaling Laws and Subnanosecond-Time-Resolution Imaging

Towards Quantitative Interpretation of Fourier-Transform Photocurrent Spectroscopy on Thin-Film Solar Cells

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