On the importance of ferroelectric domains for the performance of perovskite solar cells

Rossi, Daniele; Pecchia, Alessandro; Maur, Matthias Auf der; Leonhard, Tobias; Röhm, Holger; Hoffmann, Michael J.; Colsmann, Alexander; Carlo, Aldo Di

doi:10.1016/j.nanoen.2018.02.049

Cited by 54 publications

(65 citation statements)

References 19 publications

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“…Alternating ferroelectric domains were also confirmed on differently fabricated polycrystalline perovskite thin films, as well as on single crystals . According to the recent simulations, the electric field within the ferroelectric domains created by the spontaneous polarization produces alternating transport channels for the photogenerated electrons and holes . The charge carriers can propagate along the discrete domain boundaries toward the respective electrodes, effectively reducing recombination losses.…”

Section: Introductionmentioning

confidence: 71%

“…If the polarization influences the charge carrier recombination and transport, as was predicted by simulations, then the orientation and the shape of polarized domains within grains would directly influence the device performance. In turn, this renders the engineering of the grain orientation and size a pivotal parameter for the optimization of perovskite solar cells, which is not yet commonly investigated in most perovskite solar cell studies.…”

Section: Resultsmentioning

confidence: 92%

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Probing the Microstructure of Methylammonium Lead Iodide Perovskite Solar Cells

et al. 2019

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The microstructure of absorber layers is pivotally important for all thin‐film solar technologies. Using electron backscattered diffraction (EBSD), the crystal orientation in methylammonium lead iodide thin films with submicrometer resolution is reported. For the vast majority of (110) oriented grains, the c‐axis of the perovskite unit cell is oriented in‐plane. Although some adjacent grains exhibit the same in‐plane horizontal orientation of the c‐axis, no universal horizontal orientation of the c‐axis within the sample plane exists. The (110) crystal orientation correlates with an in‐plane orientation of the ferroelectric polarization as investigated by vertical and lateral piezoresponse force microscopy (PFM). The individual grains with different crystal orientations that exhibit different ferroelectric patterns and surface potentials are identified. The strong correlation between crystal orientation and ferroelectric polarization allows conclusions to be drawn about the microstructure from PFM measurements and, likewise, the ferroelectric polarization to be derived from crystallographic observations by EBSD.

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Section: Introductionmentioning

confidence: 71%

Section: Resultsmentioning

confidence: 92%

Probing the Microstructure of Methylammonium Lead Iodide Perovskite Solar Cells

et al. 2019

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“…[44] Assuming head-to-head and tail-to-tail orientation of the domain polarization, these simulations revealed that polarized domains in MAPbI 3 thinfilms can effectively influence charge carriers, form separate electron-and hole-pathways and hence create charged domain walls as illustrated in Figure 5. [44] Assuming head-to-head and tail-to-tail orientation of the domain polarization, these simulations revealed that polarized domains in MAPbI 3 thinfilms can effectively influence charge carriers, form separate electron-and hole-pathways and hence create charged domain walls as illustrated in Figure 5.…”

Section: Implications For Materials Designmentioning

confidence: 92%

Ferroelectric Properties of Perovskite Thin Films and Their Implications for Solar Energy Conversion

et al. 2019

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Yet, as of today, the microscopic origin of the remarkable charge carrier dynamics in perovskite solar cells remains unclear. An often proposed idea to explain the enhanced separation and transport of photogenerated charge carriers describes the formation of ferroelectric domains, i.e., domains with alternating polarization.Ferroelectric domains would provide local internal electric fields that assist with the separation of charge carriers and hence reduce recombination. [2][3][4] However, whether or not OMH perovskites are ferroelectric materials or exhibit other ferroic properties, and which effects might result from these properties have been a subject of debate for several years. A multitude of measurement techniques was employed in order to probe ferroic properties of single crystal samples, [5,6] pressed powder pellets, [7] and polycrystalline thin-films [8] of OMH perovskites. Scanning microscopy techniques such as atomic force microscopy (AFM), [9][10][11][12] scanning electron microscopy (SEM), [13] and tunneling electron microscopy (TEM) [14] were extensively used in order to reveal the microstructure of OMH-perovskite thinfilm samples with subgrain resolution. Some of these studies revealed ordered domains within crystal grains, but no consensus has been reached about the interpretation of their ferroic and crystallographic origins. Claims included piezoelectricity, [15][16][17] pyroelectricity, [5] ferroelasticity, [9,12,18] antiferroelectricity [19] as well as ferroelectricity, [10,11,15,16,20] and the seemingly contradictory reports on these ferroic properties have heated up the discussion. Techniques that probe large areas of specimens such as X-ray diffraction (XRD), [21] impedance spectroscopy, [22,23] and J-V characterization [5,7] added a rather spatially averaged picture of the samples' microstructure. For example, second harmonic generation (SHG) measurements were employed in order to identify whether or not OMH perovskites form polar crystals, but their interpretation led to ambiguous results. [5,24] In order to clarify some of the confusion and seemingly contradictory reports on the ferroic and, in particular, ferroelectric features of OMH perovskites, we review and discuss some of the fundamental properties of this material class and correlate them with our own observations on perovskite thin-films. We deliberately focus on the ferroic properties of archetypical methylammonium lead iodide (MAPbI 3 ), representing the class of light-harvesting perovskites.Whether or not methylammonium lead iodide (MAPbI 3 ) is a ferroelectric semiconductor has caused controversy in the literature, fueled by many misunderstandings and imprecise definitions. Correlating recent literature reports and generic crystal properties with the authors' experimental evidence, the authors show that MAPbI 3 thin-films are indeed semiconducting ferroelectrics and exhibit spontaneous polarization upon transition from the cubic high-temperature phase to the tetragonal phase at room temperature. The polarization is predomina...

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“…This does not least depend on the nature of the domain walls, that is, a head-to-head or a head-to-tail polarization configuration which would lead to charged or uncharged domain walls. Optoelectronic drift-diffusion modeling on charged domain walls has indicated that the microscopic electric fields within the domains may well support the spatial separation of charges and reduce their recombination [20]. These simulations also produced evidence that only in-plane oriented polarizations effectively separate electron and holes whereas any out-of-plane components have no noticeable effect.…”

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confidence: 93%

Ferroelectricity and stability measurements in perovskite solar cells

Colsmann

Röhm

2019

J. Phys. Energy

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With the ferroelectric nature of modern perovskite solar cells being more and more accepted by the community, new questions arise. How do the microscopic electric fields within the polar domains affect the device performance, and how must measurement routines be adapted to account for the ferroelectric effect within the light-harvesting layer? This becomes particularly important, if devices are measured constantly for a long time as commonly performed in solar cell ageing tests. In this perspective article, we discuss which effects may arise from creeping poling even under low driving voltages or under illumination, as well as effects from phase transitions when crossing the Curie temperature for accelerated ageing at elevated temperatures. We elucidate why ferroelectric effects must be carefully considered when assessing the lifetime of perovskite solar cells and where comparability comes to its limits.

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On the importance of ferroelectric domains for the performance of perovskite solar cells

Cited by 54 publications

References 19 publications

Probing the Microstructure of Methylammonium Lead Iodide Perovskite Solar Cells

Probing the Microstructure of Methylammonium Lead Iodide Perovskite Solar Cells

Ferroelectric Properties of Perovskite Thin Films and Their Implications for Solar Energy Conversion

Ferroelectricity and stability measurements in perovskite solar cells

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