Seeing Down to the Bottom: Nondestructive Inspection of All‐Polymer Solar Cells by Kelvin Probe Force Microscopy

Cui, Zequn; Sun, Jianxia; Landerer, Dominik; Sprau, Christian; Thelen, Richard; Colsmann, Alexander; Hölscher, Hendrik; Ma, Wanli; Chi, Lifeng

doi:10.1002/admi.201600446

Cited by 15 publications

(15 citation statements)

References 52 publications

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“…To examine the energy level alignment at the D/A heterojunction, we used Kelvin probe force microscopy (KPFM) to map the surface potential (Figure S6, Supporting Information). [48,49] The experimental setups are schemed in Figure 1c,d. For the control sample, scanning the PBDB-T surface produces an average contact potential of 734 mV, which is higher than the value of 526 mV on the IT-M surface (Figure 1c).…”

Section: Heterojunction Doping Strategymentioning

confidence: 99%

Identifying the Electrostatic and Entropy‐Related Mechanisms for Charge‐Transfer Exciton Dissociation at Doped Organic Heterojunctions

Xue

Tang

Zhou

et al. 2021

Adv Funct Materials

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The electron donor/acceptor (D/A) heterojunction is the core for photocharge generation and recombination in organic photovoltaics (OPVs). Developing practical methods for the D/A heterojunction modification remains challenging and is rarely discussed in OPV research. Herein, the roles of molecular doping at the D/A heterojunction in the charge-transfer exciton dissociation and detailed energy loss are investigated, and new insights are gained into the functions of doping on the OPV performance. Heterojunction doping simultaneously enhances all three OPV parameters, especially the short-circuit current (J sc ). It is shown that the J sc improvement is due to the combined effects of strengthened electric field and reduced activation energy, which is regulated via an entropy-related mechanism. The performance enhancement is further demonstrated in homojunction devices showing the great potential of interfacial doping to overcome the intrinsic limitation between high J sc and open-circuit voltage (V oc ) in OPVs.

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Section: Heterojunction Doping Strategymentioning

confidence: 99%

Identifying the Electrostatic and Entropy‐Related Mechanisms for Charge‐Transfer Exciton Dissociation at Doped Organic Heterojunctions

Xue

Tang

Zhou

et al. 2021

Adv Funct Materials

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“…The energetics was also estimated by simulations, [33][34][35][36] however these rely on reliable input parameters and do not substitute direct experimental measurements. Scanning Kelvin Probe Microscopy has been also applied for the study of energetic alignment in organic photovoltaic systems, [37][38][39] however this method suffers from limitations due to tip size convolution effects, complex sample preparation and doesn't offer information about the density of states (DOS) of the materials. Among the various experimental techniques offering information about the energy levels of materials, it is widely accepted that the most accurate and reliable method is photoemission spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Visualizing the Vertical Energetic Landscape in Organic Photovoltaics

Lami

Weu

Zhang

et al. 2019

Joule

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Energy level diagrams in organic electronic devices play a crucial role in device performance and interpretation of device physics. In the case of organic solar cells, it has become routine to estimate the photovoltaic gap of the donor:acceptor blend using the energy values measured on the individual blend components, resulting in a poor agreement with the corresponding open-circuit voltage of the device. To address this issue, we developed a method that allows a direct visualisation of the vertical energetic landscape in the blend, obtained by combining ultraviolet photoemission spectroscopy and argon cluster etching. We investigate both model and high-performance photovoltaic systems and demonstrate that the resulting photovoltaic gaps are in close agreement with the measured CT energies and open-circuit voltages. Furthermore, we show that this method allows us to study the evolution of the energetic landscape upon environmental degradation, critically important for understanding degradation mechanisms and development of mitigation strategies.

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“…The slope in the edge interface may be caused by the inevitable average effect from the atomic force microscope (AFM) cantilever during the measurement. In our KPFM setup, the measured CPD is opposite to the surface potential . Therefore, a surface potential decrease ψ = −66.7 mV appears in the irradiated area.…”

mentioning

confidence: 89%

Modulating the Spatial Electrostatic Potential for 1D Colloidal Nanoparticles Assembly

Chen

Huang

Toma

et al. 2017

Adv Materials Inter

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the sub-20 nm scale, is in creating highresolution prepatterns, which demand for expensive equipment and nontrivial procedures.In our previous work, we have developed a smart approach to assemble smallsize CNPs into controllable 1D arrays by lightening the effort in lithographic prepatterns. [22,23] Taking 13 nm Au nanoparticles as an example, 1D single-unit arrays can be formed on the larger-sized grooves (up to 150 nm in width) of lithographic structures. It is worth to be noticed that the final effective diameter of CNPs has to consider both the size of the rigid core (i.e., 13 nm) and a double charge layer. In particular, following the equation: κ = 3.288√I, reported by Jiang et al., [23] the thickness of the double charge layer is expected to be around 42 nm, which results in a final CNP diameter of about 97 nm. In this view, 1D nanoparticle arrays with different interparticle distances and particle sizes can be obtained by a careful tuning of the channel width. The aforementioned works have indicated that the interaction between nanoparticles and grooves, mediated by the local electrostatic potential, plays a predominant role for the high-resolution confinement of CNPs. However, experimental measurements and quantitative models of the local electrostatic potential are still necessary in order to fully comprehend and exploit its role in the precise control of 1D CNP arrays. Here, the spatially engineered electrostatic potential in grooves has been directly measured and quantitatively modeled. A novel strategy based on the synergistic modulation of lateral and bottom electrostatic potential has been demonstrated. These results are opening intriguing scenarios toward a comprehensive investigation of the 1D CNP assemble, thus highlighting exciting perspectives in the realization of quantum-controlled devices, including ultracompact circuitry, where 1D arrays of sub-20 nm CNPs are mandatory. [24] Negative-charged Au colloidal particles (core size of around 13 nm) synthesized by sodium citrate reduction of HAuCl 4 have been chosen as a typical study object. [25,26] The bottom of the trenches has been modified with positive-charged molecules, namely aminopropyltriethoxysilane (APTES), which allows for electrostatic attraction and consequently particles assembly. [27,28] It is worth to be noticed that, for the templates without APTES modification, particles cannot be deposited into them. As generally shown in previous work, [22] lateral 1D nanoparticle arrangements have gained widespread attention because of their unique collective physical properties and potential applications in functional devices. To push the device integration toward its intrinsic limits, the precise positioning of colloidal nanoparticles into 1D layout is still a challenging task, especially for nanoparticles in the sub-20 nm range. In this work, a novel strategy based on the synergistic modulation of lateral and bottom electrostatic potential of grooves is applied, thus demonstrating a high-resolution confinement of 1D colloidal nanoparticle ...

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Seeing Down to the Bottom: Nondestructive Inspection of All‐Polymer Solar Cells by Kelvin Probe Force Microscopy

Cited by 15 publications

References 52 publications

Identifying the Electrostatic and Entropy‐Related Mechanisms for Charge‐Transfer Exciton Dissociation at Doped Organic Heterojunctions

Identifying the Electrostatic and Entropy‐Related Mechanisms for Charge‐Transfer Exciton Dissociation at Doped Organic Heterojunctions

Visualizing the Vertical Energetic Landscape in Organic Photovoltaics

Modulating the Spatial Electrostatic Potential for 1D Colloidal Nanoparticles Assembly

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