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Panova O, Ophus C, Takacs CJ, Bustillo KC, Balhorn L, Salleo A, Balsara N, Minor AM. Diffraction imaging of nanocrystalline structures in organic semiconductor molecular thin films. NATURE MATERIALS 2019; 18:860-865. [PMID: 31160799 DOI: 10.1038/s41563-019-0387-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Accepted: 04/23/2019] [Indexed: 05/22/2023]
Abstract
The properties of organic solids depend on their structure and morphology, yet direct imaging using conventional electron microscopy methods is hampered by the complex internal structure of these materials and their sensitivity to electron beams. Here, we manage to observe the nanocrystalline structure of two organic molecular thin-film systems using transmission electron microscopy by employing a scanning nanodiffraction method that allows for full access to reciprocal space over the size of a spatially localized probe (~2 nm). The morphologies revealed by this technique vary from grains with pronounced segmentation of the structure-characterized by sharp grain boundaries and overlapping domains-to liquid-crystal structures with crystalline orientations varying smoothly over all possible rotations that contain disclinations representing singularities in the director field. The results show how structure-property relationships can be visualized in organic systems using techniques previously only available for hard materials such as metals and ceramics.
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Affiliation(s)
- Ouliana Panova
- Department of Materials Science and Engineering, University of California, Berkeley, CA, USA
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Colin Ophus
- National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | | | - Karen C Bustillo
- National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Luke Balhorn
- Department of Materials Science and Engineering, Stanford University, Palo Alto, CA, USA
| | - Alberto Salleo
- Department of Materials Science and Engineering, Stanford University, Palo Alto, CA, USA
| | - Nitash Balsara
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA, USA
- Joint Center for Energy Storage Research, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Andrew M Minor
- Department of Materials Science and Engineering, University of California, Berkeley, CA, USA.
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
- National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
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Kang JJ, Yang TY, Lan YK, Wu WR, Su CJ, Weng SC, Yamada NL, Su AC, Jeng US. Directed Vertical Diffusion of Photovoltaic Active Layer Components into Porous ZnO-Based Cathode Buffer Layers. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2018; 14:e1704310. [PMID: 29498203 DOI: 10.1002/smll.201704310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 01/13/2018] [Indexed: 06/08/2023]
Abstract
Cathode buffer layers (CBLs) can effectively further the efficiency of polymer solar cells (PSCs), after optimization of the active layer. Hidden between the active layer and cathode of the inverted PSC device configuration is the critical yet often unattended vertical diffusion of the active layer components across CBL. Here, a novel methodology of contrast variation with neutron and anomalous X-ray reflectivity to map the multicomponent depth compositions of inverted PSCs, covering from the active layer surface down to the bottom of the ZnO-based CBL, is developed. Uniquely revealed for a high-performance model PSC are the often overlooked porosity distributions of the ZnO-based CBL and the differential diffusions of the polymer PTB7-Th and fullerene derivative PC71 BM of the active layer into the CBL. Interface modification of the ZnO-based CBL with fullerene derivative PCBEOH for size-selective nanochannels can selectively improve the diffusion of PC71 BM more than that of the polymer. The deeper penetration of PC71 BM establishes a gradient distribution of fullerene derivatives over the ZnO/PCBE-OH CBL, resulting in markedly improved electron mobility and device efficiency of the inverted PSC. The result suggests a new CBL design concept of progressive matching of the conduction bands.
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Affiliation(s)
- Jia-Jhen Kang
- National Synchrotron Radiation Research Center, Hsinchu Science Park, Hsinchu, 30076, Taiwan
| | - Tsung-Yu Yang
- Department of Chemical Engineering, National Tsing Hua University, Hsinchu, 30013, Taiwan
| | - Yi-Kang Lan
- Materials and Electro-Optic Research Division, National Chung Shan Institute of Science and Technology, Taoyuan, 32546, Taiwan
| | - Wei-Ru Wu
- National Synchrotron Radiation Research Center, Hsinchu Science Park, Hsinchu, 30076, Taiwan
| | - Chun-Jen Su
- National Synchrotron Radiation Research Center, Hsinchu Science Park, Hsinchu, 30076, Taiwan
| | - Shih-Chang Weng
- National Synchrotron Radiation Research Center, Hsinchu Science Park, Hsinchu, 30076, Taiwan
| | - Norifumi L Yamada
- Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tokai, Naka, 319-1106, Japan
| | - An-Chung Su
- Department of Chemical Engineering, National Tsing Hua University, Hsinchu, 30013, Taiwan
| | - U-Ser Jeng
- National Synchrotron Radiation Research Center, Hsinchu Science Park, Hsinchu, 30076, Taiwan
- Department of Chemical Engineering, National Tsing Hua University, Hsinchu, 30013, Taiwan
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Cummings J, Lowengrub JS, Sumpter BG, Wise SM, Kumar R. Modeling solvent evaporation during thin film formation in phase separating polymer mixtures. SOFT MATTER 2018; 14:1833-1846. [PMID: 29451285 DOI: 10.1039/c7sm02560b] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Preparation of thin films by dissolving polymers in a common solvent followed by evaporation of the solvent has become a routine processing procedure. However, modeling of thin film formation in an evaporating solvent has been challenging due to a need to simulate processes at multiple length and time scales. In this work, we present a methodology based on the principles of linear non-equilibrium thermodynamics, which allows systematic study of various effects such as the changes in the solvent properties due to phase transformation from liquid to vapor and polymer thermodynamics resulting from such solvent transformations. The methodology allows for the derivation of evaporative flux and boundary conditions near each surface for simulations of systems close to the equilibrium. We apply it to study thin film microstructural evolution in phase segregating polymer blends dissolved in a common volatile solvent and deposited on a planar substrate. Effects of the evaporation rates, interactions of the polymers with the underlying substrate and concentration dependent mobilities on the kinetics of thin film formation are studied.
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Affiliation(s)
- John Cummings
- Department of Mathematics, The University of Tennessee, Knoxville, TN-37996, USA.
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Gedefaw D, Sharma A, Pan X, Bjuggren JM, Kroon R, Gregoriou VG, Chochos CL, Andersson MR. Optimization of the power conversion efficiency in high bandgap pyridopyridinedithiophene-based conjugated polymers for organic photovoltaics by the random terpolymer approach. Eur Polym J 2017. [DOI: 10.1016/j.eurpolymj.2017.03.044] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Fernández Garrillo PA, Borowik Ł, Caffy F, Demadrille R, Grévin B. Photo-Carrier Multi-Dynamical Imaging at the Nanometer Scale in Organic and Inorganic Solar Cells. ACS APPLIED MATERIALS & INTERFACES 2016; 8:31460-31468. [PMID: 27762134 DOI: 10.1021/acsami.6b11423] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Investigating the photocarrier dynamics in nanostructured and heterogeneous energy materials is of crucial importance from both fundamental and technological points of view. Here, we demonstrate how noncontact atomic force microscopy combined with Kelvin probe force microscopy under frequency-modulated illumination can be used to simultaneously image the surface photopotential dynamics at different time scales with a sub-10 nm lateral resolution. The basic principle of the method consists in the acquisition of spectroscopic curves of the surface potential as a function of the illumination frequency modulation on a two-dimensional grid. We show how this frequency-spectroscopy can be used to probe simultaneously the charging rate and several decay processes involving short-lived and long-lived carriers. With this approach, dynamical images of the trap-filling, trap-delayed recombination and nongeminate recombination processes have been acquired in nanophase segregated organic donor-acceptor bulk heterojunction thin films. Furthermore, the spatial variation of the minority carrier lifetime has been imaged in polycrystalline silicon thin films. These results establish two-dimensional multidynamical photovoltage imaging as a universal tool for local investigations of the photocarrier dynamics in photoactive materials and devices.
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Affiliation(s)
- Pablo A Fernández Garrillo
- Université Grenoble Alpes , F-38000 Grenoble, France
- CEA , LETI, MINATEC Campus, F-38054 Grenoble, France
- INAC-SPrAM, CEA, CNRS, Université Grenoble Alpes , F-38000 Grenoble, France
| | - Łukasz Borowik
- Université Grenoble Alpes , F-38000 Grenoble, France
- CEA , LETI, MINATEC Campus, F-38054 Grenoble, France
| | - Florent Caffy
- INAC-SPrAM, CEA, CNRS, Université Grenoble Alpes , F-38000 Grenoble, France
| | - Renaud Demadrille
- INAC-SPrAM, CEA, CNRS, Université Grenoble Alpes , F-38000 Grenoble, France
| | - Benjamin Grévin
- INAC-SPrAM, CEA, CNRS, Université Grenoble Alpes , F-38000 Grenoble, France
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