Metal Halide Perovskite Polycrystalline Films Exhibiting Properties of Single Crystals

Brenes, Roberto; Guo, Dengyang; Osherov, Anna; Noel, Nakita K.; Eames, C.; Hutter, Eline M.; Pathak, Sandeep; Niroui, Farnaz; Friend, Richard H.; Islam, M. Saïful; Snaith, Henry J.; Bulović, Vladimir; Savenije, Tom J.; Stranks, Samuel D.

doi:10.1016/j.joule.2017.08.006

Cited by 285 publications

(408 citation statements)

References 41 publications

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“…Commonly reported values for the non-radiative ( τ nr = 100 ns) and radiative ( τ rad = 2 μs) carrier lifetimes in MAPbI 3 48 , combined with the effective masses, give estimated diffusion lengths in the range of 1–10 μm, similar to values reported experimentally 13–17 and comparable with those of moderately doped GaAs 58 . Finally, both GaAs and tetragonal MAPbI 3 luminesce strongly and with a high quantum yield in surface passivated samples, clearly suggesting that the band gap of MAPbI 3 is direct 14 . The parallel between tetragonal MAPbI 3 and GaAs, two materials defining a gold standard for solar cells, is intriguing and worthy of further investigation.…”

Section: Discussionmentioning

confidence: 95%

“…Despite the rise in device performance, the origin of the exceptional transport properties of MAPbI 3 remains the subject of debate. Long carrier diffusion lengths of up to 1 μm have been recognized early on as a key factor for device performance 13 , and diffusion lengths as high as tens of microns in single crystals (and more recently in polycrystalline thin films) 14–16 have been reported. The associated long carrier lifetimes of up to tens of microseconds are also particularly surprising given that MAPbI 3 films are solution processed and polycrystalline 14,17 .…”

Section: Introductionmentioning

confidence: 99%

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Inversion symmetry and bulk Rashba effect in methylammonium lead iodide perovskite single crystals

et al. 2018

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Methylammonium lead iodide perovskite (MAPbI3) exhibits long charge carrier lifetimes that are linked to its high efficiency in solar cells. Yet, the mechanisms governing these unusual carrier dynamics are not completely understood. A leading hypothesis—disproved in this work—is that a large, static bulk Rashba effect slows down carrier recombination. Here, using second harmonic generation rotational anisotropy measurements on MAPbI3 crystals, we demonstrate that the bulk structure of tetragonal MAPbI3 is centrosymmetric with I4/mcm space group. Our calculations show that a significant Rashba splitting in the bandstructure requires a non-centrosymmetric lead iodide framework, and that incorrect structural relaxations are responsible for the previously predicted large Rashba effect. The small Rashba splitting allows us to compute effective masses in excellent agreement with experiment. Our findings rule out the presence of a large static Rashba effect in bulk MAPbI3, and our measurements find no evidence of dynamic Rashba effects.

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Section: Discussionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Inversion symmetry and bulk Rashba effect in methylammonium lead iodide perovskite single crystals

et al. 2018

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“…[8] As a unique event in the landscape of solar energy harvesting, perovskite solar cells have experienced an increment of their power conversion efficiency by ≈8% (from 13.4% to 23.7%) in the last 5 years. Solutions to guarantee the durability of products are mandatory and can be numerous, if the problem is addressed from different perspectives.Within the possible approaches to stabilize the perovskite lattice and its behavior under illumination, recent efforts have focused on introducing various treatments, [11,12] molecules, or additives, [13][14][15][16][17][18][19] through different procedures. However, the well-known structural instability of hybrid perovskites under working conditions limits a real market uptake of all the related technologies.…”

mentioning

confidence: 99%

“…Within the possible approaches to stabilize the perovskite lattice and its behavior under illumination, recent efforts have focused on introducing various treatments, [11,12] molecules, or additives, [13][14][15][16][17][18][19] through different procedures. Nitrogen has been also exploited as inert species [20][21][22][23][24] but its role is still unfocused.…”

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confidence: 99%

Nitrogen Soaking Promotes Lattice Recovery in Polycrystalline Hybrid Perovskites

Alberti

Deretzis

Mannino

et al. 2019

Advanced Energy Materials

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wide dissemination, and high technological throughput. [8] As a unique event in the landscape of solar energy harvesting, perovskite solar cells have experienced an increment of their power conversion efficiency by ≈8% (from 13.4% to 23.7%) in the last 5 years. [9,10] This technology is expected to successfully contribute to the enormous challenge of future power supply from sustainable energy sources. However, the well-known structural instability of hybrid perovskites under working conditions limits a real market uptake of all the related technologies. Solutions to guarantee the durability of products are mandatory and can be numerous, if the problem is addressed from different perspectives.Within the possible approaches to stabilize the perovskite lattice and its behavior under illumination, recent efforts have focused on introducing various treatments, [11,12] molecules, or additives, [13][14][15][16][17][18][19] through different procedures. Nitrogen has been also exploited as inert species [20][21][22][23][24] but its role is still unfocused. The existing (direct or indirect) findings in the literature stimulate the idea of beneficially using N 2 molecules in technological solutions, if their role is persuasively afforded. [25] N 2 molecules are small, safe, and easy to apply.Related to the material stability, we emphasize that the plethora of perovskites produced in different laboratories, with preparation procedures changing from lab to lab and from time to time, ask for treatments that take care and, in a certain extent, reset the starting conditions in a convenient and reproducible manner. This is particularly needed for small grained perovskite layers, on one hand used to implement pinhole-free coverages, but, on the other hand, offering extended lattice discontinuities due to the high surface to volume ratio. In addition to morphology and environment, temperature-related effects are unavoidable during device operation. [24,26] A rationalization of the phenomena needs to embody heating and thermal cycles to preserve the material integrity and/or the structural reversibility versus temperature.In this framework, we argue that nitrogen species have an active role in the stabilization of all the exposed methylammonium lead iodide (MAPbI 3 ) surfaces via their action at grain shells. This conclusion is independent of the particular On the basis of experiment and theory, a general paradigm is drawn that reconsiders N 2 not simply being an inert species but rather an effective healing gas molecule if entering a methylammonium lead iodide (MAPbI 3 ) layer. Nitrogen is soaked into polycrystalline MAPbI 3 via a postdeposition mild thermal treatment under slightly overpressure conditions to promote its diffusion across the whole layer. A significant reduction of radiative recombination and a concurrent increase of light absorption, with a maximum benefit at 80 °C, are observed. Concomitantly, the current of holes drawn from the surfaces with nanometer resolution through a biased tip is raised by a factor of 3 un...

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“…[27][28][29][30][31][32] XRD patterns, testified a complete conversion of precursors into perovskite phases. The SEF-SC protocol, avoids the usage of toxic and dangerous solvents, solving an important step of perovskite solar cell technology.…”

Section: Wwwadvmattechnoldementioning

confidence: 99%

Eco‐Friendly Spray Deposition of Perovskite Films on Macroscale Textured Surfaces

Sansoni

Bastiani

Aydın

et al. 2020

Adv Materials Technologies

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are directly realized on top of a silicon bottom cell. Utilizing commercial crystalline silicon (c-Si) wafers brings a technological challenge since the perovskite device needs then to be fabricated on wafers that feature micron-scale randomly distributed pyramidal texture, an imperative characteristic for industrial c-Si solar cells for minimizing reflection losses. The PSCs owe their present prominence to their high PCE obtained via solutiondeposition techniques, which is arguably cheaper and simpler compared to conventional vacuum-based deposition for device fabrication. From this perspective, it is required to make solution-based processing of perovskite solar cells compatible with the use of micron-scale textured substrates. Among solution processing techniques, spin coating is widespread due to its process simplicity, ease of access, and because high-quality polycrystalline perovskite films can be obtained. However, this technique is not suitable for upscaling toward industrialization. Also, considering suggestions for large-scale applications in which spin coating is translated into blade coating, the application of this technique usually results in high material consumption, which is undesirable for a sustainable low-cost production. Moreover, spin coating the perovskite layer on textured silicon bottom cells represents a challenge by itself which, to date, reportedly led to poor coverage of the films resulting in low-performing tandems. [2,3] At present, 2T tandems are mainly realized following two approaches. In the first case, the c-Si bottom cell features a mirror-polished flat front surface to accommodate spin-coated perovskite films. However, this causes reflection losses in the device, which hamper the overall PCE and require additional antireflective coatings or foils. [4] In the second case, the perovskite is deposited on textured c-Si via hybrid conversion, where the perovskite precursors, lead(II) iodide (PbI 2 ) and cesium bromide (CsBr), are thermally evaporated on the c-Si bottom cell and then converted into perovskite by spin coating the organic ammonium salts (formamidinium iodide/bromide, FAI, and FABr, respectively). [2] In this case, the limiting factor is represented by fine-tuning the conversion process. Overall, both techniques strongly rely on spin coating as a deposition/ conversion method, which still represents a roadblock toward scaling-up for commercialization. Indeed, for successful PV An innovative sequential eco-friendly spray coating (SEF-SC) technique is developed to uniformly deposit metal halide perovskite films on macroscale textured surfaces, such as textured crystalline-silicon wafers. Contrasting with previous work on spray-coated perovskite solar cells, the method presented in this work completely avoids the use of toxic and dangerous solvents. Both MAPbI 3 and CsFAMAPbI 3−x Br x perovskite films deposited by SEF-SC show excellent optoelectronic properties and no phase segregation, even when synthesized in ambient conditions. Uniform perovskite coatings are obtained...

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Metal Halide Perovskite Polycrystalline Films Exhibiting Properties of Single Crystals

Cited by 285 publications

References 41 publications

Inversion symmetry and bulk Rashba effect in methylammonium lead iodide perovskite single crystals

Inversion symmetry and bulk Rashba effect in methylammonium lead iodide perovskite single crystals

Nitrogen Soaking Promotes Lattice Recovery in Polycrystalline Hybrid Perovskites

Eco‐Friendly Spray Deposition of Perovskite Films on Macroscale Textured Surfaces

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