Characterization of Methylammonium Lead Iodide Thin Films Fabricated by Exposure of Lead Iodide Layers to Methylammonium Iodide Vapor in a Closed Crucible Transformation Process

Dachauer, Ralph; Clemens, Oliver; Lakus-Wollny, Kerstin; Mayer, Thomas; Jaegermann, Wolfram

doi:10.1002/pssa.201800894

Cited by 5 publications

(4 citation statements)

References 59 publications

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“…Figures 7 and 8 show illustrations of these possible effects of the different evaporation schemes on the electronic structure of our devices. The graphs present schematic sketches of possible band diagrams, where the placements of valence band, conduction band and Fermi level correspond to the literature data as measured by PES in references 24,[29][30][31][32][33] .…”

Section: Discussionmentioning

confidence: 99%

“…Two thought models potentially explaining the influence of the sequential evaporations schemes on the measured performance have been portrayed. The first model presumes the evaporation of an unconverted PbI 2 layer to create an energy barrier for the holes in the p-i-n structure due to the mismatched band offset 24,[29][30][31][32][33] . This would be beneficial at the ETL interface (post deposition of PbI 2 ), but not desirable at the HTL side.…”

Section: Discussionmentioning

confidence: 99%

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Impact of dynamic co-evaporation schemes on the growth of methylammonium lead iodide absorbers for inverted solar cells

Heidrich

Berwig

et al. 2022

Sci Rep

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A variety of different synthesis methods for the fabrication of solar cell absorbers based on the lead halide perovskite methylammonium lead iodide (MAPbI3, MAPI) have been successfully developed in the past. In this work, we elaborate upon vacuum-based dual source co-evaporation as an industrially attractive processing technology. We present non-stationary processing schemes and concentrate on details of co-evaporation schemes where we intentionally delay the start/end points of one of the two evaporated components (MAI and PbI2). Previously, it was found for solar cells based on a regular n-i-p structure, that the pre-evaporation of PbI$$_2$$ 2 is highly beneficial for absorber growth and solar cell performance. Here, we apply similar non-stationary processing schemes with pre/post-deposition sequences for the growth of MAPI absorbers in an inverted p-i-n solar cell architecture. Solar cell parameters as well as details of the absorber growth are compared for a set of different evaporation schemes. Contrary to our preliminary assumptions, we find the pre-evaporation of PbI2 to be detrimental in the inverted configuration, indicating that the beneficial effect of the seed layers originates from interface properties related to improved charge carrier transport and extraction across this interface rather than being related to an improved absorber growth. This is further evidenced by a performance improvement of inverted solar cell devices with pre-evaporated MAI and post-deposited PbI2 layers. Finally, we provide two hypothetical electronic models that might cause the observed effects.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Impact of dynamic co-evaporation schemes on the growth of methylammonium lead iodide absorbers for inverted solar cells

Heidrich

Berwig

et al. 2022

Sci Rep

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“…In Figure 5, for the pristine MAPI (step 1/), peaks measured at 402.6 eV (N 1s), 285.00 eV (C 1s), 138.6 eV (Pb 4f 7/2 ), and 619.6 eV (I 3d 5/2 ) are characteristic of n-type MAPI and in agreement with the literature. 19,35,36 The characteristic energy difference of ca. 283.5 eV between the VBM onset and the main C 1s emission places the Fermi level 1.5 eV above the VBM.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Photoelectron Spectroscopy of Co-evaporated and Spin-Coated LiTFSI-Doped Spiro-OMeTAD Reveals the Interface Energetics Inside a MAPI-based Perovskite Solar Cell

Maheu,

Hellmann,

Prabowo

et al. 2023

J. Phys. Chem. C

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The electronic doping mechanism of the Spiro-OMeTAD (2,2′,7,7′-Tetrakis[N,N-di(4-methoxyphenyl)amino]-9 , 9 ′ -s p i r o b i fl u o r e n e ) w i t h L i T F S I ( l i t h i u m b i s -(trifluoromethylsulfonyl)imide) and tBP (4-tert-Butylpyridine) has not been fully understood. Spiro-OMeTAD is a highly studied hole transport layer in solar cells and, especially, perovskite solar cells (PSCs). Its p-doping not only improves the hole transport characteristics and thus the photocurrent but also increases the band bending at the interface with the perovskite absorber and thus the cell photovoltage. A better understanding of the p-doping of Spiro-OMeTAD and its interface energetics with MAPI would contribute to optimization strategies for a better overall efficiency of the PSC. Until now, doping mechanisms were studied separately for liquid and thermal evaporation processing. It was impossible to pinpoint the similarities and differences between the two approaches. Using an integrated ultra-high vacuum cluster tool (DAISY-SOL), we prepared LiTFSI-doped Spiro-OMeTAD samples by spincoating under an inert atmosphere and by thermal co-evaporation in a vacuum. Without contact with the atmosphere, the thin films were then characterized by photoelectron spectroscopy to deduce their electronic properties. It has been evidenced that with thermal co-evaporation, LiTFSI alone dopes the Spiro-OMeTAD layer, while for spin-coating, the additive tBP is required to prevent LiTFSI precipitation. Both processes give a more p-doped Spiro-OMeTAD layer by shifting its Fermi level toward the highest occupied molecular orbital (HOMO) at best by 0.65 eV. This results in a final energy difference between the Fermi level and the HOMO onset of 0.4 eV for the most p-doped sample. The co-evaporation process of LiTFSI and Spiro-OMeTAD was then used to perform interface experiments of doped Spiro-OMeTAD on MAPI and of Au on doped Spiro-OMeTAD to study a simplified solar cell structure SnO 2 | MAPI | Spiro-OMeTAD | Au. Results confirm that the band alignment is suitable for electron blocking and hole extraction. Under light, a surface photovoltage of at least 0.65 eV is measured at the MAPI | Spiro-OMeTAD interface, making it the functional key interface. These interface experiments provide a not only detailed but also quantitative picture of the band alignment both in the dark and in operation under illumination under open circuit conditions.

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“…The PSC samples selected were manufactured as part of the material development of the Surface Science Group of the Technical University of Darmstadt, aiming for the optimization of PSC's performances to the physical optimum (Dachauer et al, 2019;Mortan et al, 2019Mortan et al, , 2020Wittich et al, 2018). They represent a typical PSC device, including several FunMats and manufacturing processes (Figure 4) commonly used in many research labs (Chen et al, 2017).…”

Section: Case Study Descriptionmentioning

confidence: 99%

Scheme for generating upscaling scenarios of emerging functional materials based energy technologies in prospective LCA (UpFunMatLCA)

Weyand

Kawajiri

Mortan

et al. 2023

J of Industrial Ecology

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Upscaling scenarios are indispensable elements of prospective life cycle assessment (LCA). However, current studies reveal confusing terminology and a wide range of approaches in this area. Therefore, we first defined the term upscaling scenario as the description of a possible future target stage of emerging technology, including the development pathway from a current stage within the course of research and development to this future stage. Second, we developed the novel systematic scheme UpFunMatLCA for generating explorative scenarios based on possible development pathways of the specific group of emerging functional material (FunMat)-based energy technologies, including status quo developments. UpFunMatLCA represents a threestep extension of conventional LCAs to upscale the life cycle inventory of emerging FunMats. UpFunMatLCA is based on a clear definition of a current status quo (conceptual, lab, or pilot stage) and a target matured (fab) development stage. A core part of UpFunMatLCA is the so-called upscaling module, providing specific modeling methods and data for the upscaling of FunMats. Using perovskite solar cells, photovoltaic devices based on several FunMats and attached with great expectations regarding the future efficient provision of solar energy, we demonstrate the application of UpFun-MatLCA, focusing on the upstream greenhouse gas (GHG) emissions of the prospective manufacturing. In the discussion, we point out the application area of UpFunMatLCA and the possible extension to depict further environmental impacts beyond GHG to contribute to the sustainability assessment of emerging technologies in the early stages of development.

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Characterization of Methylammonium Lead Iodide Thin Films Fabricated by Exposure of Lead Iodide Layers to Methylammonium Iodide Vapor in a Closed Crucible Transformation Process

Cited by 5 publications

References 59 publications

Impact of dynamic co-evaporation schemes on the growth of methylammonium lead iodide absorbers for inverted solar cells

Impact of dynamic co-evaporation schemes on the growth of methylammonium lead iodide absorbers for inverted solar cells

Photoelectron Spectroscopy of Co-evaporated and Spin-Coated LiTFSI-Doped Spiro-OMeTAD Reveals the Interface Energetics Inside a MAPI-based Perovskite Solar Cell

Scheme for generating upscaling scenarios of emerging functional materials based energy technologies in prospective LCA (UpFunMatLCA)

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