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AFM for Solar, Photovoltaics and Thermoelectrics Research

AFM image showing the photoconductive properties of a photovoltaic material

Photovoltaic (PV), thermoelectric (TE), and related materials and devices are developing rapidly and branching into many varying fields, including PV polymers, traditional semiconductor based PV devices, and now perovskite PV materials. Realizing a future of plentiful, low-cost renewable energy is within reach but requires improved characterization of next-generation photovoltaic (PV) materials. Essential to this effort are the high-resolution imaging capabilities of atomic force microscopy (AFM). Asylum Research atomic force microscopes provide platforms for all of the major types of PV materials and devices at every stage of their development, including transparent materials, opaque materials, illumination from the top and bottom, and use of external, user-provided light source. Our electrical characterization suite, combined with our broad platform set, and topped off by our wide array of software and hardware customization tools are unmatched in the AFM industry.

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Kelvin Probe Force Microscopy (KPFM)

  • Accurately measures surface contact potential difference (CPD) based on differences in the photo- or thermally- excited current

Electrostatic Force Microscopy (EFM)

  • Maps variations in the gradient of the capacitance locally. Changes in photo- or thermally-excited current as a function of time can be observed using this technique

Scanning Microwave Impedance Microscopy (sMIM)

  • Maps variations in local capacitance and resistance, allowing the scientist to see photo-current on 'floating' materials, or PV materials not built into a device

Conductive AFM (CAFM)

  • Measures current through the tip as a function of an applied sample bias and as a function of illumination strength or temperature

Current Mapping with Fast Force Mapping

  • Measures current at an applied sample bias during the contact segment of a fast force curve, allowing imaging of delicate PV materials without damage

KPFM

    • Measure change in local charge (~50-100 nm) variation when a sample is illuminated or heated
    • Find variations in local work function with light or heat
    • Map local domains in some materials that have n and p regions
    • Watch the change in local photo- or thermo- current with time by watching the change in potential

EFM

    • Watch the change in capacitance gradient of a sample with time after illumination or heating
    • Map the change in capacitance gradient of a sample with changes in heat or light

CAFM

  • Map photo and thermal current quantitatively
  • Map changes in mobility as a sample is illuminated
  • Map domains of variation in electron charge using fast forces with current mapping, or fast current mapping (FCM)
  • Temporally measure photo and thermal current in samples
  • Map current in domain walls in perovskite materials for PV applications

sMIM

  • Characterize a wide range of linear and non-linear materials, including conductors, semiconductors, and insulators, allowing an in depth view of PV and PT materials and devices
  • Provide contrast based on material permittivity and conductivity
  • Visualize buried structures based on capacitance variations measured at the surface
  • Map photo and thermal current on isolated PV materials

N. Beaumont, S. W. Cho, P. Sullivan, D. Newby, K. E. Smith, and T. S. Jones, "Boron Subphthalocyanine Chloride as an Electron Acceptor for High-Voltage Fullerene-Free Organic Photovoltaics," Adv. Funct. Mater. 22, 561-566 (2011). doi:10.1002/adfm.201101782

V. W. Bergmann, S. A. L. Weber, F. J. Ramos, M. K. Nazeeruddin, M. Grätzel, D. Li, A. L. Domanski, I. Lieberwirth, S. Ahmad, and R. Berger, "Real-space observation of unbalanced charge distribution inside a perovskite-sensitized solar cell," Nat. Commun. 5, 5001 (2014). doi:10.1038/ncomms6001

J. H. Choi, K.-I. Son, T. Kim, K. Kim, K. Ohkubo, and S. Fukuzumi, "Thienyl-substituted methanofullerene derivatives for organic photovoltaic cells," J. Mater. Chem. 20, 475-482 (2010). doi:10.1039/b916597e

D. C. Coffey, and D. S. Ginger, "Time-resolved electrostatic force microscopy of polymer solar cells," Nat. Mater. 5, 735-740 (2006). doi:10.1038/nmat1712

D. C. Coffey, O. G. Reid, D. B. Rodovsky, G. P. Bartholomew, and D. S. Ginger, "Mapping Local Photocurrents in Polymer/Fullerene Solar Cells with Photoconductive Atomic Force Microscopy," Nano Lett. 7, 738-744 (2007). doi:10.1021/nl062989e

A. Fejfar, M. Hývl, M. Ledinský, A. Vetushka, J. Stuchlk, J. Kočka, S. Misra, B. O'Donnell, M. Foldyna, L. Yu, and P. R. i Cabarrocas, "Microscopic measurements of variations in local (photo)electronic properties in nanostructured solar cells," Sol. Energy Mater. Sol. Cells 119, 228-234 (2013). doi:10.1016/j.solmat.2013.07.042

I. Hancox, K. V. Chauhan, P. Sullivan, R. A. Hatton, A. Moshar, C. P. A. Mulcahy, and T. S. Jones, "Increased efficiency of small molecule photovoltaic cells by insertion of a MoO3 hole-extracting layer," Energy Environ. Sci. 3, 107-110 (2010). doi:10.1039/b915764f

C. V. Hoven, X.-D. Dang, R. C. Coffin, J. Peet, T.-Q. Nguyen, and G. C. Bazan, "Improved Performance of Polymer Bulk Heterojunction Solar Cells Through the Reduction of Phase Separation via Solvent Additives," Adv. Mater. 22, E63-E66 (2010). doi:10.1002/adma.200903677

V. S. Kale, R. R. Prabhakar, S. S. Pramana, M. Rao, C.-H. Sow, K. B. Jinesh, and S. G. Mhaisalkar, "Enhanced electron field emission properties of high aspect ratio silicon nanowire–zinc oxide core–shell arrays," Phys. Chem. Chem. Phys. 14, 4614 (2012). doi:10.1039/c2cp40238f

D. A. Kamkar, M. Wang, F. Wudl, and T.-Q. Nguyen, "Single Nanowire OPV Properties of a Fullerene-Capped P3HT Dyad Investigated Using Conductive and Photoconductive AFM," ACS Nano 6, 1149-1157 (2012). doi:10.1021/nn204565h

J. H. Kim, P.-W. Liang, S. T. Williams, N. Cho, C.-C. Chueh, M. S. Glaz, D. S. Ginger, and A. K.-Y. Jen, "High-Performance and Environmentally Stable Planar Heterojunction Perovskite Solar Cells Based on a Solution-Processed Copper-Doped Nickel Oxide Hole-Transporting Layer," Adv. Mater. 27, 695-701 (2014). doi:10.1002/adma.201404189

Y. Liang, D. Feng, Y. Wu, S.-T. Tsai, G. Li, C. Ray, and L. Yu, "Highly Efficient Solar Cell Polymers Developed via Fine-Tuning of Structural and Electronic Properties," J. Am. Chem. Soc. 131, 7792-7799 (2009). doi:10.1021/ja901545q

F. Liu, W. Zhao, J. R. Tumbleston, C. Wang, Y. Gu, D. Wang, A. L. Briseno, H. Ade, and T. P. Russell, "Understanding the Morphology of PTB7:PCBM Blends in Organic Photovoltaics," Adv. Energy Mater. 4, 1301377 (2013). doi:10.1002/aenm.201301377

F. Ma, Y. Ou, Y. Yang, Y. Liu, S. Xie, J.-F. Li, G. Cao, R. Proksch, and J. Li, "Nanocrystalline Structure and Thermoelectric Properties of Electrospun NaCo2O4 Nanofibers," J. Phys. Chem. C 114, 22038-22043 (2010). doi:10.1021/jp107488k

L. S. C. Pingree, B. A. MacLeod, and D. S. Ginger, "The Changing Face of PEDOT:PSS Films: Substrate, Bias, and Processing Effects on Vertical Charge Transport," J. Phys. Chem. C 112, 7922-7927 (2008). doi:10.1021/jp711838h

L. S. C. Pingree, O. G. Reid, and D. S. Ginger, "Imaging the Evolution of Nanoscale Photocurrent Collection and Transport Networks during Annealing of Polythiophene/Fullerene Solar Cells," Nano Lett. 9, 2946-2952 (2009). doi:10.1021/nl901358v

S. C. Price, A. C. Stuart, and W. You, "Low Band Gap Polymers Based on Benzo[1,2-b:4,5-b']dithiophene: Rational Design of Polymers Leads to High Photovoltaic Performance," Macromolecules 43, 4609-4612 (2010). doi:10.1021/ma100051v

O. G. Reid, K. Munechika, and D. S. Ginger, "Space Charge Limited Current Measurements on Conjugated Polymer Films using Conductive Atomic Force Microscopy," Nano Lett. 8, 1602-1609 (2008). doi:10.1021/nl080155l

S. Schumann, R. A. Hatton, and T. S. Jones, "Organic Photovoltaic Devices Based on Water-Soluble Copper Phthalocyanine," J. Phys. Chem. C 115, 4916-4921 (2011). doi:10.1021/jp109544m

G. Shao, M. S. Glaz, F. Ma, H. Ju, and D. S. Ginger, "Intensity-Modulated Scanning Kelvin Probe Microscopy for Probing Recombination in Organic Photovoltaics," ACS Nano 8, 10799-10807 (2014). doi:10.1021/nn5045867

H. M. Stec, R. J. Williams, T. S. Jones, and R. A. Hatton, "Ultrathin Transparent Au Electrodes for Organic Photovoltaics Fabricated Using a Mixed Mono-Molecular Nucleation Layer," Adv. Funct. Mater. 21, 1709-1716 (2011). doi:10.1002/adfm.201002021

T. Sun, J. Ma, Q. Yan, Y. Huang, J. Wang, and H. Hng, "Influence of pulsed laser deposition rate on the microstructure and thermoelectric properties of Ca3Co4O9 thin films," J. Cryst. Growth 311, 4123-4128 (2009). doi:10.1016/j.jcrysgro.2009.06.044

N. K. Unsworth, I. Hancox, C. A. Dearden, T. Howells, P. Sullivan, R. S. Lilley, J. Sharp, and T. S. Jones, "Highly conductive spray deposited poly(3, 4-ethylenedioxythiophene):poly (styrenesulfonate) electrodes for indium tin oxide-free small molecule organic photovoltaic devices," Appl. Phys. Lett. 103, 173304 (2013). doi:10.1063/1.4826651

P. Zhao, J. Xu, H. Wang, L. Wang, W. Kong, W. Ren, L. Bian, and A. Chang, "Calcium manganate: A promising candidate as buffer layer for hybrid halide perovskite photovoltaic-thermoelectric systems," J. Appl. Phys. 116, 194901 (2014). doi:10.1063/1.4901636