Alkylammonium lead halides. Part 1. Isolated PbI64− ions in (CH3NH3)4PbI6•2H2O

Vincent, Beverly R.; Robertson, Katherine N.; Cameron, T. Stanley; Knop, Osvald

doi:10.1139/v87-176

Cited by 192 publications

(134 citation statements)

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“…19 These crystals have previously been reported to be obtained from aqueous solutions of Pb(NO 3 ) 2 and CH 3 NH 3 I. 20 The water molecules observed in our crystals were most likely introduced by exposing the sample to air. This result again supports the importance of the use of dehydrated solvents and starting materials for the preparation of the perovskite layers, as the procedure to obtain perovskite crystals from the reaction of an excess amount of CH 3 NH 3 I with PbI 2 is comparable to that on the surface of our films during the dipping process.…”

Section: ¹1mentioning

confidence: 61%

Reproducible Fabrication of Efficient Perovskite-based Solar Cells: X-ray Crystallographic Studies on the Formation of CH₃NH₃PbI₃ Layers

et al. 2014

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Lead halide complexes formed during the fabrication of perovskite (CH 3 NH 3 PbI 3 )-based solar cells were examined by single-crystal X-ray diffraction analysis. Based on the observed results, the fabrication protocol using a sequential deposition method was optimized to reproducibly provide highly efficient solar cells with power conversion efficiencies of more than 10%. ) and vapor deposition processes, 7 have been reported for the formation of perovskite layers. In this work, we used a sequential deposition method and examined the influence of the purity of the starting materials on the formation of the resulting perovskite layers in solar cells with high PCEs. Moreover, we report the results of single-crystal X-ray diffraction analyses conducted on lead halide complexes, which are potentially formed during the production process. Based on the results obtained, the fabrication protocol for the solar cells was optimized. We found that for the reproducible fabrication of highly efficient perovskite solar cells, the water content of lead iodide (PbI 2 ) as the starting material is crucial. Our optimized method uses dehydrated PbI 2 and thus enables the highly reproducible fabrication of solar cells with PCEs of more than 10%.To minimize the influence of water and oxygen, we prepared the perovskite and hole-transporting layers in an inert glovebox (Ar; H 2 O and O 2 , <0.1 ppm) using dehydrated (H 2 O, <8 ppm) N,N-dimethylformamide (DMF), 2-propanol, and chlorobenzene. Otherwise, the solar cells were fabricated according to literature procedures.6 Patterned transparent conducting oxide substrates (FTO, 25 mm © 25 mm) were covered with a compact TiO 2 layer by spray pyrolysis of bis(acetylacetonato)titanium diisopropoxide in ethanol (0.05 M) at 450°C.6,15 Subsequent spin-coating of an ethanol suspension of a TiO 2 paste (PST-18NR, TiO 2 paste:ethanol = 1:3.5 wt ratio) resulted in the deposition of ca. 200 nm-thick-mesoporous films of TiO 2 nanoparticles (particle diameter: ca. 20 nm). In an Ar-filled glovebox, PbI 2 was then introduced into the TiO 2 nanopores by spin-coating a solution of PbI 2 in DMF (1.01.1 M) at 70°C. Upon drying (70°C, 1 h), the films turned to deep yellow. Afterwards, the films were dipped for 20 s in a 0.06 M solution of CH 3 NH 3 I in 2-propanol. During this process, the color of the films turned to red-black from the corner of the square substrates (see movie in the SI 16). This may be attributed to the slightly nonhomogeneous distributions of the PbI 2 loadings on the substrate surface during the spin-coating process. The films were quickly rinsed with 2-propanol and dried (70°C, 30 min). The hole-transporting layer was deposited on the perovskite layer by spin-coating a solution of 2,2¤,7,7¤-tetrakis(N,N-di-p-methoxyphenylamine)-9,9¤-spirobifluorene (spiro-OMeTAD) in chlorobenzene (0.058 M) containing 4-tert-butylpyridine (0.19 M) and lithium bis(trifluoromethylsulfonyl)imide (0.031 M) as well as tris[2-(1H-pyrazol-1-yl)-4-tert-butylpyridine]cobalt(III) tris[bis(trifluoromethylsulfonyl...

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Section: ¹1mentioning

confidence: 61%

Reproducible Fabrication of Efficient Perovskite-based Solar Cells: X-ray Crystallographic Studies on the Formation of CH₃NH₃PbI₃ Layers

et al. 2014

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“…14 Figure S4, characteristic reflection at 2θ = 11.39° in XRD pattern in Figure 2a) Figure 2d). 15 The simulated XRD pattern in Figure 2a shows that this compound has a diffraction peak around 11.4°. Papavassiliou et al reported the value of 3.87 eV for the position of the bandgap of (CH 3 NH 3 ) 4 PbI 6 •2H 2 O by optical absorption spectroscopy.…”

Section: Equationmentioning

confidence: 99%

Reversible Hydration of CH₃NH₃PbI₃ in Films, Single Crystals, and Solar Cells

et al. 2015

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Solar cells comprising methylammonium lead iodide perovskite (MAPI) are notorious for their sensitivity to moisture. We show that hydrated crystal phases are formed when MAPI is exposed to water vapour at room temperature and that these phase changes are fully reversed when the material is subsequently dried. The reversible formation of CH 3 NH 3 PbI 3 •H 2 O followed by (CH 3 NH 3 ) 4 PbI 6 •2H 2 O (upon long exposure times) was observed using time resolved XRD and ellipsometry of thin films prepared using 'solvent engineering', single crystals, and state of the art solar cells. In contrast to water vapour, the presence of liquid water results in the irreversible decomposition of MAPI to form PbI 2 . MAPI changes from dark brown to transparent on hydration; the precise optical constants of CH 3 NH 3 PbI 3 •H 2 O formed on single crystals were determined, with a bandgap at 3.1 eV. Using the single crystal optical constants and thin film ellipsometry measurements, the time dependent changes to MAPI films exposed to moisture were modelled. The results suggest that the mono-hydrate phase forms independently of the depth in the film suggesting rapid transport of water molecules along grain boundaries. Vapour phase hydration of an unencapsulated solar cell (initially J sc ≈ 19 mA cm -2 and V oc ≈ 1.05 V at 1 sun) resulted in more than a 90 % drop in short circuit photocurrent and around 200 mV loss in open circuit potential, but these losses were fully reversed after the cell was exposed to dry nitrogen for 6 hours. Hysteresis in the current-voltage characteristics was significantly increased after this dehydration, which may be related to changes in the defect density and morphology of MAPI following recrystallization from the hydrate. Based on our observations we suggest that irreversible decomposition of MAPI in the presence of water vapour only occurs significantly once a grain has been fully converted to the hydrate phase.

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“…[228][229][230][231][232] The crystal structure formed depends on the humidity content, temperature, and exposure time, with the initial formation of a monohydrated phase, followed by the formation of a dihydrated crystal phase. The water incorporation process appears to be isotropic, meaning that it occurs more or less homogeneously throughout the sample, rather than crystallization beginning at the outside and moving inwards, suggesting that water is highly mobile within the lattice and/ or along grain boundaries.…”

Section: Moisturementioning

confidence: 99%

Capturing the Sun: A Review of the Challenges and Perspectives of Perovskite Solar Cells

Petrus

Schlipf

Cheng

et al. 2017

Advanced Energy Materials

317

201

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following statement: These materials can be processed from solution and yet exhibit optoelectronic materials properties described in classic solid-state physics textbooks. This unprecedented combination has led to photovoltaic devices that can be processed at room temperature and achieve performance levels similar to industry giant polycrystalline silicon, from a starting point of 3.8% in 2009. [1][2][3][4] The first light-emitting electrochemical cells [5] and diodes [6][7][8] have also been introduced recently, leading to tunable light emission spectra and internal quantum efficiencies exceeding 15%.The road towards these achievements has been marked by a constant improvement of perovskite deposition techniques fueled by our increasing understanding of the crystallization processes. The choice of deposition technique, either from solution or vapor, and the composition and order in which precursor species are applied has a great influence on the crystallization kinetics. Here, one can distinguish one-step methods where the perovskite is formed from a precursor mixture dissolved in a common solution, and two-step methods where the inorganic compound is deposited first and transformed to the perovskite phase later by addition of the organic constituents. [9][10][11] Furthermore, many parameters during processing can have an effect on the crystallization mechanism and consequently on film morphology, such as the choice of solvents, concentrations and processing additives that are often not incorporated into the final product. [11][12][13] We discuss this aspect in Section 2, where we focus our attention on the most commonly employed solution-based techniques. Additionally, as for any new technology trying to displace an incumbent technology, higher efficiencies, lower costs, reproducibility, stability, and sustainability are paramount. In particular, reproducibility has been a major challenge in perovskite solar cells from the beginning: small variations in morphology, like crystal size, film roughness, and pinholes can have detrimental effects on photovoltaic performance. [14] On the other hand, current-voltage measurements often showed a hysteresis that is rarely seen in other photovoltaic technologies. [15] These topics are highlighted in Sections 3 and 4. Finally, in Section 5 we discuss the framework for market introduction, such as cost reduction by choosing low-cost charge transport layers, or how the lifetime of perovskite absorbers can be extended by the choice of materials composition.Hybrid metal halide perovskites have become one of the hottest topics in optoelectronic materials research in recent years. Not only have they surpassed everyone's expectations and achieved similar performance as tried and true polycrystalline silicon photovoltaic devices, but they are also finding applications in a variety of different fields, including lighting. The main advantages of hybrid metal halide perovskites are simple processability, compatible with large-scale solution processing such as roll-to-roll printing, a...

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Alkylammonium lead halides. Part 1. Isolated PbI₆⁴⁻ ions in (CH₃NH₃)₄PbI₆•2H₂O

Cited by 192 publications

References 1 publication

Reproducible Fabrication of Efficient Perovskite-based Solar Cells: X-ray Crystallographic Studies on the Formation of CH₃NH₃PbI₃ Layers

Reproducible Fabrication of Efficient Perovskite-based Solar Cells: X-ray Crystallographic Studies on the Formation of CH₃NH₃PbI₃ Layers

Reversible Hydration of CH₃NH₃PbI₃ in Films, Single Crystals, and Solar Cells

Capturing the Sun: A Review of the Challenges and Perspectives of Perovskite Solar Cells

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Alkylammonium lead halides. Part 1. Isolated PbI64− ions in (CH3NH3)4PbI6•2H2O

Cited by 192 publications

References 1 publication

Reproducible Fabrication of Efficient Perovskite-based Solar Cells: X-ray Crystallographic Studies on the Formation of CH3NH3PbI3 Layers

Reproducible Fabrication of Efficient Perovskite-based Solar Cells: X-ray Crystallographic Studies on the Formation of CH3NH3PbI3 Layers

Reversible Hydration of CH3NH3PbI3 in Films, Single Crystals, and Solar Cells

Capturing the Sun: A Review of the Challenges and Perspectives of Perovskite Solar Cells

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Alkylammonium lead halides. Part 1. Isolated PbI₆⁴⁻ ions in (CH₃NH₃)₄PbI₆•2H₂O

Reproducible Fabrication of Efficient Perovskite-based Solar Cells: X-ray Crystallographic Studies on the Formation of CH₃NH₃PbI₃ Layers

Reproducible Fabrication of Efficient Perovskite-based Solar Cells: X-ray Crystallographic Studies on the Formation of CH₃NH₃PbI₃ Layers

Reversible Hydration of CH₃NH₃PbI₃ in Films, Single Crystals, and Solar Cells