Kelvin Probe Force Microscopy Study on Conjugated Polymer/Fullerene Bulk Heterojunction Organic Solar Cells

Hoppe, Harald; Glatzel, Thilo; Niggemann, Michael; Hinsch, Andreas; Lux‐Steiner, M.; Sariciftci, Niyazi Serdar

doi:10.1021/nl048176c

Cited by 279 publications

(282 citation statements)

References 50 publications

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“…31 During casting and subsequent annealing processes, there is a process of crystallization, alignment of polymer chains, and limited self-organization, which changes the structure to favor exciton collection and charge transport. 50,51 This process is extremely sensitive to the solvent used, 52,53 variations in composition, 54 annealing, [55][56][57][58][59] chemical-structure variations, [60][61][62][63] purities, 64 and processing conditions, 65 to name but a few of the related parameters when dealing with what is a fundamentally unstable system. 66 The seminal work by Yang et al demonstrated the necessity of controlled mixing of the acceptor and donor in the composite.…”

Section: Brief Overview Of Bulk-heterojunction Opvsmentioning

confidence: 99%

Block copolymer strategies for solar cell technology

Topham¹,

Parnell²,

Hiorns³

2011

J Polym Sci B Polym Phys

186

169

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A simple overview of the methods used and the expected benefits of block copolymers in organic photovoltaic devices is given in this review. The description of the photovoltaic process makes it clear how the detailed self-assembly properties of block copolymers can be exploited. Organic photovoltaic technology, an inexpensive, clean and renewable energy source, is an extremely promising option for replacing fossil fuels. It is expected to deliver printable devices processed on flexible substrates using high-volume techniques. Such devices, however, currently lack the long-term stability and efficiency to allow organic photovoltaics to surpass current technologies. Block copolymers are envisaged to help overcome these obstacles because of their long term structural stability and their solid-state morphology being of the appropriate dimensions to efficiently perform charge collection and transfer to electrodes.

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Section: Brief Overview Of Bulk-heterojunction Opvsmentioning

confidence: 99%

Block copolymer strategies for solar cell technology

Topham¹,

Parnell²,

Hiorns³

2011

J Polym Sci B Polym Phys

186

169

View full text Add to dashboard Cite

show abstract

“…It has been applied to characterize various types of solids used in electronic devices such as ionic crystal thin films, 2 semiconductors, 3 organic solar cell structures, 4 and nanographenes 5 in order to study the sample lateral variations of surface potentials and work functions and infer the electronic structures.…”

Section: Introductionmentioning

confidence: 99%

Simulating and interpreting Kelvin probe force microscopy images on dielectrics with boundary integral equations

Shen

Barnett

Pinsky

2008

Review of Scientific Instruments

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Reduced leakage current, enhanced ferroelectric and dielectric properties in (Ce,Fe)-codoped Na0.5Bi0.5TiO3 film Appl. Phys. Lett. 100, 022909 (2012) Modified Johnson model for ferroelectric lead lanthanum zirconate titanate at very high fields and below Curie temperature Appl. Phys. Lett. 100, 022907 (2012) Engineering titanium and aluminum oxide composites using atomic layer deposition J. Appl. Phys. 110, 123514 (2011) High dielectric tunability of (100) oriented PbxSr1xTiO3 thin film coordinately controlled by dipole activation and phase anisotropy J. Appl. Phys. 110, 124107 (2011) Kelvin probe force gradient microscopy of charge dissipation in nano thin dielectric layers J. Appl. Phys. 110, 084304 (2011) Additional information on Rev. Sci. Instrum. Kelvin probe force microscopy ͑KPFM͒ is designed for measuring the tip-sample contact potential differences by probing the sample surface, measuring the electrostatic interaction, and adjusting a feedback circuit. However, for the case of a dielectric ͑insulating͒ sample, the contact potential difference may be ill defined, and the KPFM probe may be sensing electrostatic interactions with a certain distribution of sample trapped charges or dipoles, leading to difficulty in interpreting the images. We have proposed a general framework based on boundary integral equations for simulating the KPFM image based on the knowledge about the sample charge distributions ͑forward problem͒ and a deconvolution algorithm solving for the trapped charges on the surface from an image ͑inverse problem͒. The forward problem is a classical potential problem, which can be efficiently solved using the boundary element method. Nevertheless, the inverse problem is ill posed due to data incompleteness. For some special cases, we have developed deconvolution algorithms based on the forward problem solution. As an example, this algorithm is applied to process the KPFM image of a gadolinia-doped ceria thin film to solve for its surface charge density, which is a more relevant quantity for samples of this kind than the contact potential difference ͑normally only defined for conductive samples͒ values contained in the raw image.

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“…KPFM is a method working in combination with nc-AFM and which is based on the minimization of the electrostatic interaction between the tip and the sample. Electrostatic tip-sample interactions have been widely studied in the long-range regime on the experimental and on the theoretical level [23][24][25][26][27][28][29] within the frame of nc-AFM and KPFM [30][31][32][33][34] . Long-range electrostatic forces cause capacitive forces connected to the capacitance of the tip/counter-electrode capacitor as well as Coulombic forces connected to the presence of charges within it.…”

Section: Introductionmentioning

confidence: 99%

Polarization effects in noncontact atomic force microscopy: A key to model the tip-sample interaction above charged adatoms

2011

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We discuss the influence of short-range electrostatic forces, so called dipolar forces, between the tip of an atomic force microscope (AFM) and a surface carrying charged adatoms. Dipolar forces are of microscopic character and have their origin in the polarizability of the foremost atoms on tip and surface. In most experiments performed by non-contact AFM, other forces such as binding forces dominate the interaction. However, in the experiments presented by Gross et al. [Science 324, 1428[Science 324, (2009, where the charge state of individual gold atoms adsorbed on a thin dielectric layer was determined, binding forces are negligible as the tip-sample distance is relatively large.We develop a model which mimics the experimental tip-sample geometry of the aforementioned experiments. The model includes van der Waals and long-range electrostatic interactions, as well as the short-range electrostatic interaction based on the self-consistent description of electronic polarization effects on neutral and charged adatoms. The model is based on a calculation of the electrostatic energy of the tip-sample geometry.Our calculations of non-contact AFM imaging as well as of bias spectroscopic curves are in good agreement with the experimental ones presented by Gross et al. It is demonstrated that the short-range dipolar force is mainly responsible for the contrast observed in topography imaging above charged species. However, it is the long-range capacitive force which is responsible for the detection of the charge state in bias spectroscopy. We discuss implications of our findings on future experiments which aim to detect single charges by means of Kelvin probe force microscopy.

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Kelvin Probe Force Microscopy Study on Conjugated Polymer/Fullerene Bulk Heterojunction Organic Solar Cells

Cited by 279 publications

References 50 publications

Block copolymer strategies for solar cell technology

Block copolymer strategies for solar cell technology

Simulating and interpreting Kelvin probe force microscopy images on dielectrics with boundary integral equations

Polarization effects in noncontact atomic force microscopy: A key to model the tip-sample interaction above charged adatoms

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