Engineering solar cells based on correlative X-ray microscopy

Stückelberger, Michael; West, Bradley; Nietzold, Tara; Lai, Barry; Mäser, J.; Rose, Volker; Bertoni, Mariana I.

doi:10.1557/jmr.2017.108

Cited by 62 publications

(80 citation statements)

References 133 publications

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“…[106] Depending on the solar cell that is being characterized, charge separation occurs by an internal p-n junction or due to the charge-carriers collected by the selective contacts. Both of these techniques measure current, and in the case of XBIC, this is proportional to the number of absorbed X-ray photons.…”

Section: X-ray Beam Induced Currentmentioning

confidence: 99%

“…This method showed the relation between the material composition and electronic performance for perovskite thin-films for the first time. [106] Therefore, stoichiometry changes in the film can be related and measured in parallel with charge collection efficiency. XBIC current measures were taken at the same time as XRF scans; degradation in the XBIC data was observed because of the X-ray beam intensity.…”

Section: Halide Heterogeneity and Stoichiometrymentioning

confidence: 99%

“…Measurements were realized using the APS, at ANL, with an X-ray beam of 9 keV photon energy, focused to a spot size of 40 nm FWHM with a photon flux of 8 × 10 8 photons s −1 . [106] According to Stuckelberger et al [107] the regions of high and low I are considered as regions of maximum or minimum perovskite layer thickness, and thus higher XBIC signal. For this reason, a new method was proposed where two scans were done for each region; the first one fast and attenuating the photon flux with an aluminum filter to 35%.…”

Section: Halide Heterogeneity and Stoichiometrymentioning

confidence: 99%

“…For this reason, a new method was proposed where two scans were done for each region; the first one fast and attenuating the photon flux with an aluminum filter to 35%. [106]. [86,107] Images were obtained displaying a region of 6 µm 2 for the distribution of Pb, I, and Ti, and the XBIC signal for the same region.…”

Section: Halide Heterogeneity and Stoichiometrymentioning

confidence: 99%

“…This solar cell did not have a HSL and had previously performed well with this architecture. [106] Specifically, the relationship between halide distribution and carrier collection was observed when plotting the normalized XBIC, as being divided into 10 × 10 boxes, and plotting it against the corresponding average Br:Pb ratio. [88] The heterogeneity observed in the XRF maps for this study is relevant due to a large range and standard deviation of the Br:Pb ratios.…”

Section: Halide Heterogeneity and Stoichiometrymentioning

confidence: 99%

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Imaging and Mapping Characterization Tools for Perovskite Solar Cells

Hidalgo

Castro‐Méndez

Correa‐Baena

2019

Advanced Energy Materials

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define the perovskite structure, decreases below 0.8 and orthorhombic, rhombohedral, or tetragonal structures tend to form. For large A-cations, layered 2D [3] and 1D [4] chain structures can be formed, e.g., Ruddlesden-Popper, Aurivillius, and Dion-Jacobson phases. Both 3D and 2D perovskites have gained the attention of the solar cell community.Lead halide perovskites are outstanding semiconductors with impressive optoelectronic properties, such as high absorption coefficient, tunable band gap, and long charge carrier lifetimes. Despite having such impressive properties, there is still a need for deeper understanding of the degradation mechanisms of the perovskite materials in order to make PSCs viable for outdoor applications and commercialization. [5,6] Currently, a major challenge facing perovskites is their long-term stability, due to their sensitivity to temperature, moisture, oxygen, and ultraviolet (UV) light. [6] Furthermore, chemical and electronic stability, compositional, and crystal homogeneity in the absorber layer of PSCs are parameters that allow us to understand and ensure the maximum PCE and long-term durability of the devices.Imaging and mapping characterization techniques allow researchers to obtain insights of the nano-and microscale features related to their chemical and electronic properties, which in turn limit PSC performance and long-term durability. This review will focus on the progress of the imaging and mapping techniques that have been used understanding and designing perovskite materials. This comprehensive review will span from basic morphology characterization methods, such as scanning electron microscopy (SEM) to advanced, synchrotron-based characterization using X-ray microscopy, such as X-ray fluorescence for compositional mapping, and X-ray beam induced current (XBIC) for electric performance mapping. Different imaging and mapping tools allow for correlations of different physical, chemical, optical and electrical features in space and time. These characterization techniques have helped explain phenomena that govern perovskite materials, including chemical and electrical properties and how they relate to solar cell performance. The following table summarizes the different imaging and mapping characterization techniques and their use for PSCs research.Perovskite solar cells (PSCs) have attracted much attention as efficiencies have gone beyond 24%. To achieve these impressive numbers, the PSC scientific community is working to improve the perovskite optoelectronic properties. Imaging and mapping characterization techniques have been widely used to understand the fundamental properties that allow lead halide perovskites to achieve high performance. In this review, these techniques are evaluated, from simple tools, such as electron microscopy, to more complex systems that include atomic force microscopy, synchrotron-based X-ray mapping, and ultrafast and photoluminescence mapping. These tools have helped understand lead halide perovskites and their impressive optoelectronic prope...

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Section: X-ray Beam Induced Currentmentioning

confidence: 99%

Section: Halide Heterogeneity and Stoichiometrymentioning

confidence: 99%

Section: Halide Heterogeneity and Stoichiometrymentioning

confidence: 99%

Section: Halide Heterogeneity and Stoichiometrymentioning

confidence: 99%

Section: Halide Heterogeneity and Stoichiometrymentioning

confidence: 99%

See 3 more Smart Citations

Imaging and Mapping Characterization Tools for Perovskite Solar Cells

Hidalgo

Castro‐Méndez

Correa‐Baena

2019

Advanced Energy Materials

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The Relationship between Chemical Flexibility and Nanoscale Charge Collection in Hybrid Halide Perovskites

Luo

Aharon

Stückelberger

et al. 2018

Adv Funct Materials

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Hybrid organometal halide perovskites are known for their excellent optoelectronic functionality as well as their wide-ranging chemical flexibility. The composition of hybrid perovskite devices has trended toward increasing complexity as fine-tuned properties are pursued, including multielement mixing on the constituents A and B and halide sites. However, this tunability presents potential challenges for charge extraction in functional devices. Poor consistency and repeatability between devices may arise due to variations in composition and microstructure. Within a single device, spatial heterogeneity in composition and phase segregation may limit the device from achieving its performance potential. This review details how the nanoscale elemental distribution and charge collection in hybrid perovskite materials evolve as chemical complexity increases, highlighting recent results using nondestructive operando synchrotron-based X-ray nanoprobe techniques. The results reveal a strong link between local chemistry and charge collection that must be controlled to develop robust, high-performance hybrid perovskite materials for optoelectronic devices.applications including solar cells, [1,2] lightemitting diodes, [3] lasers, [4] and photodetectors. [5] The exceptional minority carrier diffusion lengths in these materials [6,7] lead to nearly 100% internal quantum efficiency [8] which results in high charge-carrier collection efficiency and high external luminescence efficiency in electron-photon conversion devices. [9] Particularly in the field of photovoltaics (PV), their extraordinary material properties [10][11][12] have enabled perovskite solar absorbers to achieve large improvements in device performance in the past 8 years. The perovskite crystal structure is shown in Figure 1a, where the A-site is CH 3 NH 3 + (MA, methylammonium), the B-site is Pb 2+ , and the X-site is I − following the general perovskite formula ABX 3. After demonstration of a device with 3.8% power conversion efficiency (PCE) by Miyasaka and co-workers in a dye-sensitized solar cell architecture using CH 3 NH 3 PbI 3 , [13] a breakthrough in perovskite photovoltaics occurred in 2012 when the first allsolid-state hybrid perovskite devices were shown by Kim et al., [14] improving the chemical stability of the perovskite and enabling device performance to exceed beyond 9% using CH 3 NH 3 PbI 3 perovskites. With intense investigation of perovskite material properties from research groups all over the world, including bandgap engineering by halide mixing [15,16] and device optimization using A-site mixing, [9,17] the record PCE of hybrid perovskite solar cells reached 22.7% in 2017 after achieving 22.1% PCE in 2015 [18] using a mixture of formamidinium lead iodide (CH(NH 2 ) 2 PbI 3 ) with 5% loading of methylammonium lead bromide (CH 3 NH 3 PbBr 3 ) chemistry. [19,20] Surpassing 22% PCE by leveraging the chemical flexibility of the perovskite structure brought hybrid perovskite solar cells on par in efficiency with most polycrystalline solar absor...

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Direct Observation of Halide Migration and its Effect on the Photoluminescence of Methylammonium Lead Bromide Perovskite Single Crystals

et al. 2017

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Optoelectronic devices based on hybrid perovskites have demonstrated outstanding performance within a few years of intense study. However, commercialization of these devices requires barriers to their development to be overcome, such as their chemical instability under operating conditions. To investigate this instability and its consequences, the electric field applied to single crystals of methylammonium lead bromide (CH NH PbBr ) is varied, and changes are mapped in both their elemental composition and photoluminescence. Synchrotron-based nanoprobe X-ray fluorescence (nano-XRF) with 250 nm resolution reveals quasi-reversible field-assisted halide migration, with corresponding changes in photoluminescence. It is observed that higher local bromide concentration is correlated to superior optoelectronic performance in CH NH PbBr . A lower limit on the electromigration rate is calculated from these experiments and the motion is interpreted as vacancy-mediated migration based on nudged elastic band density functional theory (DFT) simulations. The XRF mapping data provide direct evidence of field-assisted ionic migration in a model hybrid-perovskite thin single crystal, while the link with photoluminescence proves that the halide stoichiometry plays a key role in the optoelectronic properties of the perovskite.

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Engineering solar cells based on correlative X-ray microscopy

Abstract: Abstract

Cited by 62 publications

References 133 publications

Imaging and Mapping Characterization Tools for Perovskite Solar Cells

Imaging and Mapping Characterization Tools for Perovskite Solar Cells

The Relationship between Chemical Flexibility and Nanoscale Charge Collection in Hybrid Halide Perovskites

Direct Observation of Halide Migration and its Effect on the Photoluminescence of Methylammonium Lead Bromide Perovskite Single Crystals

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