Scanning probe microscopy of solar cells: From inorganic thin films to organic photovoltaics

O’Dea, James R.; Brown, Louisa M.; Hoepker, Nikolas; Marohn, John A.; Sadewasser, Sascha

doi:10.1557/mrs.2012.143

Cited by 32 publications

(22 citation statements)

References 90 publications

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“…However, scanning probe microscopy (SPM) techniques offer a unique advantage to correlate changes in optoelectronic properties and PV performance parameters with morphological features on the nanoscale. SPM techniques have been employed to characterize other PV technologies such as silicon, copper indium gallium selenide (CIGS), CdTe, GaAs, and organic solar cells . Open‐circuit voltage variation due to grain orientation and grain boundaries was revealed .…”

Section: Introductionmentioning

confidence: 99%

Scanning Probe Microscopy Applied to Organic–Inorganic Halide Perovskite Materials and Solar Cells

et al. 2017

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preparation can lead to a large variety of film morphologies.OHPs have impressive optoelectronic properties, ranging from high absorption coefficient and suitable bandgap for visible light, [5] low exciton binding energy, [6,7] high carrier mobility, and long carrier diffusion lengths, [8] all of which make this class of materials especially suitable for PV applications. It is of the utmost importance to understand the effect that film morphology has on these critical properties, and subsequently on standard solar cell device parameters such as photocurrent, photovoltage, and PCE. OHP devices are also known to degrade under prolonged exposure to environmental factors including moisture, iodine vapor, high temperature, and sunlight. [9][10][11][12] Understanding how and why the film morphology and performance changes over time is also of key interest.Perovskite films are often characterized using conventional techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), quantum efficiency measurements, and I-V curve measurements, which lack high spatial resolution. However, scanning probe microscopy (SPM) techniques offer a unique advantage to correlate changes in optoelectronic properties and PV performance parameters with morphological features on the nanoscale. SPM techniques have been employed to characterize other PV technologies such as silicon, copper indium gallium selenide (CIGS), CdTe, GaAs, and organic solar cells. [13][14][15][16][17][18][19][20][21][22] Open-circuit voltage variation due to grain orientation and grain boundaries was revealed. [13] Moreover, SPM has been used to investigate the interfacial properties in polycrystalline Si [14] as well as in blended [15] and phase-segregated [16] organic solar cells. Furthermore, scanning-probe techniques demonstrated their ability to study molecules used for dye sensitized solar cells down to the atomic level. [20,21] In addition, SPM techniques can provide insight into phenomenon specific to OHPs. This includes film growth variation depending on fabrication technique, film degradation due to environmental factors, and undesirable current-voltage hysteresis possibly induced by ion migration within the OHP film. A wide variety of SPM techniques have been used to explore heterogeneities in OHP thin film properties (Figure 1a-c), including topographic atomic force micro scopy (AFM), Kelvin probe force microscopy (KPFM), scanning tunneling microscopy (STM), conductive-AFM (c-AFM), and scanning near-field optical microscopy (SNOM).To meet the increasing energy demands of the growing society, environmentally friendly and renewable energy sources are needed. Organicinorganic halide perovskites are a promising class of materials for building solar cells due to their easy fabrication, flexibility, and bandgap tunability. The highest efficiency achieved with these materials in the lab is comparable to conventional silicon solar cells currently on the market. However, their commercialization is hampered by certain challenges, such as stabil...

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Section: Introductionmentioning

confidence: 99%

Scanning Probe Microscopy Applied to Organic–Inorganic Halide Perovskite Materials and Solar Cells

et al. 2017

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“…The recently developed technique of photoconductive AFM (PC-AFM) builds upon C-AFM by including a one-sun light source incident on the lower surface of a transparent sample, underneath the tip location. Here “one-sun” refers to the light approximating solar illumination, since PC-AFM is commonly used on materials for photovoltaic applications [ 21 ]. This gives access to nanoscale photocurrent measurements at the sample surface, allowing us to probe carrier behaviour under illumination.…”

Section: Introductionmentioning

confidence: 99%

Characterisation of InGaN by Photoconductive Atomic Force Microscopy

et al. 2018

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Nanoscale structure has a large effect on the optoelectronic properties of InGaN, a material vital for energy saving technologies such as light emitting diodes. Photoconductive atomic force microscopy (PC-AFM) provides a new way to investigate this effect. In this study, PC-AFM was used to characterise four thick (∼130 nm) InxGa1−xN films with x = 5%, 9%, 12%, and 15%. Lower photocurrent was observed on elevated ridges around defects (such as V-pits) in the films with x≤12%. Current-voltage curve analysis using the PC-AFM setup showed that this was due to a higher turn-on voltage on these ridges compared to surrounding material. To further understand this phenomenon, V-pit cross sections from the 9% and 15% films were characterised using transmission electron microscopy in combination with energy dispersive X-ray spectroscopy. This identified a subsurface indium-deficient region surrounding the V-pit in the lower indium content film, which was not present in the 15% sample. Although this cannot directly explain the impact of ridges on turn-on voltage, it is likely to be related. Overall, the data presented here demonstrate the potential of PC-AFM in the field of III-nitride semiconductors.

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“…In this case the distance between the AFM tip and the surface can be written as (1) where d is the instantaneous tip-sample distance, h is the equilibrium tip position, A is the oscillation amplitude, f is the oscillation frequency and τ is time. Since there is no tip-surface con-tact, we consider a tunnelling current between the tip and the surface, which we approximate with an exponential function of the distance [21], (2) where σ is a linear scaling parameter and K provides the rate of exponential decay. Inserting Equation 1 into Equation 2 we obtain an expression for the tunnelling current with respect to time:…”

Section: Case 1: Dynamic Noncontact Current Measurement With Ideal Simentioning

confidence: 99%

“…Conductive atomic force microscopy (C-AFM), a contact-mode technique, has been extensively utilized to investigate local electrical properties of nanoscale systems, such as organic solar cells [1][2][3][4][5][6][7], semiconductors [8][9][10], and metals [11][12][13]. C-AFM has been used to characterize local charge transport characteristics [4,6] and to obtain detailed information about local charge mobility [5,7].…”

Section: Introductionmentioning

confidence: 99%

Current measurements in the intermittent-contact mode of atomic force microscopy using the Fourier method: a feasibility analysis

Uluutku

Solares

2020

Beilstein J. Nanotechnol.

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Atomic force microscopy (AFM) is an important tool for measuring a variety of nanoscale surface properties, such as topography, viscoelasticity, electrical potential and conductivity. Some of these properties are measured using contact methods (static contact or intermittent contact), while others are measured using noncontact methods. Some properties can be measured using different approaches. Conductivity, in particular, is mapped using the contact-mode method. However, this modality can be destructive to delicate samples, since it involves continuously dragging the cantilever tip on the surface during the raster scan, while a constant tip–sample force is applied. In this paper we discuss a possible approach to develop an intermittent-contact conductive AFM mode based on Fourier analysis, whereby the measured current response consists of higher harmonics of the cantilever oscillation frequency. Such an approach may enable the characterization of soft samples with less damage than contact-mode imaging. To explore its feasibility, we derive the analytical form of the tip–sample current that would be obtained for attractive (noncontact) and repulsive (intermittent-contact) dynamic AFM characterization, and compare it with results obtained from numerical simulations. Although significant instrumentation challenges are anticipated, the modelling results are promising and suggest that Fourier-based higher-harmonics current measurement may enable the development of a reliable intermittent-contact conductive AFM method.

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Scanning probe microscopy of solar cells: From inorganic thin films to organic photovoltaics

Abstract: Abstract

Cited by 32 publications

References 90 publications

Scanning Probe Microscopy Applied to Organic–Inorganic Halide Perovskite Materials and Solar Cells

Scanning Probe Microscopy Applied to Organic–Inorganic Halide Perovskite Materials and Solar Cells

Characterisation of InGaN by Photoconductive Atomic Force Microscopy

Current measurements in the intermittent-contact mode of atomic force microscopy using the Fourier method: a feasibility analysis

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