Multimodal noncontact atomic force microscopy and Kelvin probe force microscopy investigations of organolead tribromide perovskite single crystals

Almadori, Y.; Moerman, David; Martinez, Jaume Llacer; Leclère, Philippe; Grévin, Benjamin

doi:10.3762/bjnano.9.161

Cited by 25 publications

(33 citation statements)

References 38 publications

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“…This latter experiment helps distinguish work function change due to the SPV response from the slower, long lasting, decrease in the work function, which occurs simultaneously during the blue laser irradiation sequence. [19] Although the mechanism leading to the present surface degradation is still unclear, we can speculate that it is related to the degradation of other perovskite surfaces exposed to supragap irradiation in vacuum. [30,31] The sign of the SPV signal indicates that the sample exhibits a downward band bending of at least 90 meV.…”

Section: Surface Band Bendingmentioning

confidence: 99%

“…Surface band bending is detected using Kelvin probe force microscopy (KPFM) under various illumination conditions. [19] Using these data, an energy diagram of the material is drawn and general implications for RPPs are discussed. To our knowledge, this study represents the first comprehensive determination of the electronic levels of an n > 1 RPP perovskite.…”

Section: Introductionmentioning

confidence: 99%

“…In this work, we use ultraviolet photoelectron spectroscopy (UPS) and inverse photoelectron spectroscopy (IPES) in conjunction with density functional theory (DFT) calculations of the density of states to map out the electron and the hole transport levels in BA 2 CsPb 2 I 7 . Surface band bending is detected using Kelvin probe force microscopy (KPFM) under various illumination conditions . Using these data, an energy diagram of the material is drawn and general implications for RPPs are discussed.…”

Section: Introductionmentioning

confidence: 99%

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Quantum Well Energetics of an n = 2 Ruddlesden–Popper Phase Perovskite

Silver

Dai

et al. 2019

Advanced Energy Materials

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the metal-halide active layer from the degradation pathways that plague 3D MHPs. RPP devices have so far achieved efficiencies greater than 16% as the active layer of a solar cell with improved stability over their 3D counterparts. [6,7] Additionally, RPPs have served in conjunction with 3D perovskites as capping layers, improving the ambient stability of the system. [8,9] MHPs exhibit a great deal of tunability, with multiple options for cations (e.g., methylammonium (MA), formamidinium (FA), Cs, Rb, metals (Pb, Sn), and halides (I, Br, Cl), allowing for optimization of the band gap, charge carrier lifetimes, and structural stability. The quantum well structure of the RPPs adds several additional degrees of tunability to the energetics, including the well thickness, barrier thickness, and the nature of the organic ligand. The well thickness, controlled by the number of consecutive layers of Pb-halide octahedra, modulates the band gap and the exciton binding energy (E B ) by defining the quantum confinement of the charge carriers in the material. [10,11] The barrier thickness controls the level of electronic communication between various quantum wells. [12] The organic ligand, in addition to determining the barrier thickness, controls the height of the energetic barrier of the quantum wells, and out-ofplane mobility. [13] In order to harness the tunability and design appropriate RPPs for each application, a deeper understanding of how tuning these quantum wells affects their energetics is needed.The direct experimental determination of ionization energy [10] (IE) and electron affinity (EA) [14] has been reported for two 2D n = 1 RPPs, but not for higher order (n > 1) materials. These RPPs present a challenge in the fabrication of phase pure films for surface sensitive measurements, as the materials often comprise phases with different n's. Electron spectroscopy investigations of 2D RPPs that focus on single particle transport levels, and thus IE and EA, are necessary, as the relatively large exciton binding energy (E B ≈ 100s meV) in these materials precludes the derivation of a transport gap from optical absorption measurements. The present study focuses on the energetics of high purity films of the n = 2 RPP, butylammonium cesium lead iodide, (BA 2 CsPb 2 I 7 ). [15] Solar cell devices based on this material have previously been shown to maintain 92% of their PCE after 30 days of continuous operation in ambient conditions. [16] Using cesium instead of methylammonium increases the thermal stability [17] and charge carrier lifetimes. [18] A comprehensive investigation of the electronic energy levels of an n = 2 Ruddlesden-Popper phase perovskite is presented. Ultraviolet and inverse photoemission spectroscopies are used to probe the density of states in the valence and conduction bands, respectively, of the quasi-2D perovskite, butylammonium cesium lead iodide (BA 2 CsPb 2 I 7 ). By comparing experimental spectra with calculated projected density of states, the contributions from Cs, Pb, and I to the quantum well...

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Section: Surface Band Bendingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Quantum Well Energetics of an n = 2 Ruddlesden–Popper Phase Perovskite

Silver

Dai

et al. 2019

Advanced Energy Materials

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“…The surface photovoltage (SPV), which can be seen as a local measurement of V OC in semiconductors [ 12 ], has been studied using KPFM under modulated illumination. Indeed, the investigation of the SPV evolution as a function of a frequency-modulated excitation source can be used to access the photo-carrier dynamics in organic, inorganic and hybrid semiconductors [ 3 – 9 13 ]. In short, as depicted in Fig.…”

Section: Methodsmentioning

confidence: 99%

Numerical analysis of single-point spectroscopy curves used in photo-carrier dynamics measurements by Kelvin probe force microscopy under frequency-modulated excitation

Garrillo¹,

Grévin²,

Borowik³

2018

Beilstein J. Nanotechnol.

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In recent years, the investigation of the complex interplay between the nanostructure and photo-transport mechanisms has become of crucial importance for the development of many emerging photovoltaic technologies. In this context, Kelvin probe force microscopy under frequency-modulated excitation has emerged as a useful technique for probing photo-carrier dynamics and gaining access to carrier lifetime at the nanoscale in a wide range of photovoltaic materials. However, some aspects about the data interpretation of techniques based on this approach are still the subject of debate, for example, the plausible presence of capacitance artifacts. Special attention shall also be given to the mathematical model used in the data-fitting process as it constitutes a determining aspect in the calculation of time constants. Here, we propose and demonstrate an automatic numerical simulation routine that enables to predict the behavior of spectroscopy curves of the average surface photovoltage as a function of a frequency-modulated excitation source in photovoltaic materials, enabling to compare simulations and experimental results. We describe the general aspects of this simulation routine and we compare it against experimental results previously obtained using single-point Kelvin probe force microscopy under frequency-modulated excitation over a silicon nanocrystal solar cell, as well as against results obtained by intensity-modulated scanning Kelvin probe microscopy over a polymer/fullerene bulk heterojunction device. Moreover, we show how this simulation routine can complement experimental results as additional information about the photo-carrier dynamics of the sample can be gained via the numerical analysis.

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“…Thus, there is a need for correlative studies to link multiple nanoscale material properties. [ 2a,3f,12 ] In this work, we use the terminology correlation to establish the effect of one material property (e.g., chemical) on another (such as electrical). For example, recently, peak force infrared microscopy was implemented to relate local mechanical and chemical properties of a variety of materials, including perovskite crystals.…”

Section: Introductionmentioning

confidence: 99%

Correlated Electrical and Chemical Nanoscale Properties in Potassium‐Passivated, Triple‐Cation Perovskite Solar Cells

Tennyson

Abdi‐Jalebi

et al. 2020

Adv Materials Inter

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Perovskite semiconductors are an exciting class of materials due to their promising performance outputs in photovoltaic devices. To boost their efficiency further, researchers introduce additives during sample synthesis, such as KI. However, it is not well understood how KI changes the material and, often, leaves precipitants. To fully resolve the role of KI, multiple microscopy techniques are applied and the electrical and chemical behavior of a Reference (untreated) and a KI‐treated perovskite are compared. Upon correlation between electrical and chemical nanoimaging techniques, it is discovered that these local properties are linked to the macroscopic voltage enhancement of the KI‐treated perovskite. The heterogeneity revealed in both the local electrical and chemical responses indicates that the additive partially migrates to the surface, yet surprisingly does not deteriorate the performance locally, rather, the voltage response homogeneously increases. The research presented within provides a diagnostic methodology, which connects the nanoscale electrical and chemical properties of materials, relevant to other perovskites, including multication and Pb‐free alternatives.

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Multimodal noncontact atomic force microscopy and Kelvin probe force microscopy investigations of organolead tribromide perovskite single crystals

Cited by 25 publications

References 38 publications

Quantum Well Energetics of an n = 2 Ruddlesden–Popper Phase Perovskite

Quantum Well Energetics of an n = 2 Ruddlesden–Popper Phase Perovskite

Numerical analysis of single-point spectroscopy curves used in photo-carrier dynamics measurements by Kelvin probe force microscopy under frequency-modulated excitation

Correlated Electrical and Chemical Nanoscale Properties in Potassium‐Passivated, Triple‐Cation Perovskite Solar Cells

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