Determination of active layer morphology in all-polymer photovoltaic cells

This study investigates the structure of films spin-coated from blends of the semiconducting polymers poly(3-hexylthiophene-2,5-diyl) (P3HT) and poly{2,6-[4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]dithiophene]-alt-4,7(2,1,3-benzo­thiadiazole)} (PCPDTBT). Such blends are of potential use in all-polymer solar cells in which both the acceptor and the donor material generate excitons to contribute to the photocurrent. Prompted by threefold performance gains seen in polymer/fullerene and polymer blend solar cells upon addition of pristine graphene, devices are prepared from P3HT/PCPDTBT blends both with and without graphene. This report focuses on the morphology of the active layer since this is of critical importance in determining performance. Small-angle neutron scattering (SANS) is utilized to study this polymer blend with deuterated P3HT to provide contrast and permit the investigation of buried structure in neat and graphene-doped films. SANS reveals the presence of P3HT crystallites dispersed in an amorphous blend matrix of P3HT and PCPDTBT. The crystallites are approximately disc shaped and do not show any evidence of higher-order structure or aggregation. While the structure of the films does not change with the addition of graphene, there is a perceptible effect on the electronic properties and energy conversion efficiency in solar cells made from such films. Determination of the active layer morphology yields crucial insight into structure–property relationships in organic photovoltaic devices.

[1]  Yan Jin,et al.  Three-fold improvement in the performance of all-polymer photovoltaic devices with graphene , 2015 .

[2]  A. Ferrari,et al.  Enhanced performance of polymer:fullerene bulk heterojunction solar cells upon graphene addition , 2014 .

[3]  M. Dadmun,et al.  Tuning the Morphology and Performance of Low Bandgap Polymer:Fullerene Heterojunctions via Solvent Annealing in Selective Solvents , 2014 .

[4]  P. F. Peterson,et al.  Mantid - Data Analysis and Visualization Package for Neutron Scattering and $μ SR$ Experiments , 2014, 1407.5860.

[5]  Sean C. Smith,et al.  The isotopic effects of deuteration on optoelectronic properties of conducting polymers , 2014, Nature Communications.

[6]  M. Dadmun,et al.  Important thermodynamic characteristics of poly(3-hexyl thiophene) , 2014 .

[7]  J. Keum,et al.  Morphological origin for the stratification of P3HT:PCBM blend film studied by neutron reflectometry , 2013 .

[8]  Ian E. Jacobs,et al.  Correlating dilute solvent interactions to morphology and OPV device performance , 2013 .

[9]  Shuai Guo,et al.  Evolution of lateral structures during the functional stack build-up of P3HT:PCBM-based bulk heterojunction solar cells. , 2013, ACS applied materials & interfaces.

[10]  Florian S. U. Fischer,et al.  Influence of Processing Solvents on Optical Properties and Morphology of a Semicrystalline Low Bandgap Polymer in the Neutral and Charged States , 2013 .

[11]  V. Kuppa,et al.  Enhancement in the performance of organic photovoltaic devices with pristine graphene , 2013 .

[12]  R. Friend,et al.  Crystallization-Induced 10-nm Structure Formation in P3HT/PCBM Blends , 2013 .

[13]  Antonio Facchetti,et al.  Polymer donor–polymer acceptor (all-polymer) solar cells , 2013 .

[14]  M. Dadmun,et al.  Precise Structural Development and its Correlation to Function in Conjugated Polymer: Fullerene Thin Films by Controlled Solvent Annealing , 2013 .

[15]  Christopher B. Stanley,et al.  Polymer Chain Shape of Poly(3-alkylthiophenes) in Solution Using Small-Angle Neutron Scattering , 2013 .

[16]  A. Hexemer,et al.  Signatures of Multiphase Formation in the Active Layer of Organic Solar Cells from Resonant Soft X-ray Scattering. , 2013, ACS macro letters.

[17]  E. A. Payzant,et al.  Solvent quality-induced nucleation and growth of parallelepiped nanorods in dilute poly(3-hexylthiophene) (P3HT) solution and the impact on the crystalline morphology of solution-cast thin film , 2013 .

[18]  A. Iwan,et al.  Perspectives of applied graphene: Polymer solar cells , 2012 .

[19]  T. P. Russell,et al.  Multi‐Length‐Scale Morphologies in PCPDTBT/PCBM Bulk‐Heterojunction Solar Cells , 2012 .

[20]  W. Su,et al.  Small- and Wide-Angle X-ray Scattering Characterization of Bulk Heterojunction Polymer Solar Cells with Different Fullerene Derivatives , 2012 .

[21]  M. Dadmun,et al.  The miscibility and depth profile of PCBM in P3HT: thermodynamic information to improve organic photovoltaics. , 2012, Physical chemistry chemical physics : PCCP.

[22]  Scott A. Mauger,et al.  Investigating the Morphology of Polymer/Fullerene Layers Coated Using Orthogonal Solvents , 2012 .

[23]  D. Adamson,et al.  Stabilization of graphene sheets by a structured benzene/hexafluorobenzene mixed solvent. , 2012, Journal of the American Chemical Society.

[24]  M. Sommer,et al.  Solvent Additive Control of Morphology and Crystallization in Semiconducting Polymer Blends , 2012, Advanced materials.

[25]  A. Hexemer,et al.  Polymer Crystallization of Partially Miscible Polythiophene/Fullerene Mixtures Controls Morphology , 2011 .

[26]  M. Dadmun,et al.  A new model for the morphology of P3HT/PCBM organic photovoltaics from small-angle neutron scattering: rivers and streams. , 2011, ACS nano.

[27]  Amy M. Ballantyne,et al.  The role of alkane dithiols in controlling polymer crystallization in small band gap polymer:Fullerene solar cells , 2011 .

[28]  D. Nordlund,et al.  P3HT/PCBM bulk heterojunction organic photovoltaics: correlating efficiency and morphology. , 2011, Nano letters.

[29]  A. Heeger,et al.  Semiconducting polymers: the Third Generation. , 2010, Chemical Society reviews.

[30]  Vladimir Dyakonov,et al.  Polymer–fullerene bulk heterojunction solar cells , 2010, 1003.0359.

[31]  Neil C. Greenham,et al.  Conjugated‐Polymer Blends for Optoelectronics , 2009 .

[32]  Pete R. Jemian,et al.  Irena: tool suite for modeling and analysis of small‐angle scattering , 2009 .

[33]  F. Gröhn,et al.  Switchable nanoassemblies from macroions and multivalent dye counterions. , 2008, Chemistry.

[34]  Christoph J. Brabec,et al.  Bipolar Charge Transport in PCPDTBT‐PCBM Bulk‐Heterojunctions for Photovoltaic Applications , 2008 .

[35]  Yang Yang,et al.  Manipulating regioregular poly(3-hexylthiophene) : [6,6]-phenyl-C61-butyric acid methyl ester blends—route towards high efficiency polymer solar cells , 2007 .

[36]  A. Balankin,et al.  Scaling properties of randomly folded plastic sheets. , 2007, Physical review. E, Statistical, nonlinear, and soft matter physics.

[37]  Daniel Moses,et al.  Photoconductivity of a Low‐Bandgap Conjugated Polymer , 2007 .

[38]  R. Friend,et al.  Role of intermolecular coupling in the photophysics of disordered organic semiconductors: aggregate emission in regioregular polythiophene. , 2007, Physical review letters.

[39]  Christoph J. Brabec,et al.  High Photovoltaic Performance of a Low‐Bandgap Polymer , 2006 .

[40]  Joong Tark Han,et al.  Single‐Crystal Polythiophene Microwires Grown by Self‐Assembly , 2006 .

[41]  Maxim Shkunov,et al.  High ambipolar and balanced carrier mobility in regioregular poly(3-hexylthiophene) , 2004 .

[42]  Andre K. Geim,et al.  Electric Field Effect in Atomically Thin Carbon Films , 2004, Science.

[43]  V. Arrighi,et al.  Structural investigation of polymers by neutron scattering , 2004 .

[44]  G. Beaucage Determination of branch fraction and minimum dimension of mass-fractal aggregates. , 2004, Physical review. E, Statistical, nonlinear, and soft matter physics.

[45]  C. Glinka Methods of X-Ray and Neutron Scattering in Polymer Science, by Ryong-Joon Roe , 2001 .

[46]  B. Gabryś Applications of Neutron Scattering to Soft Condensed Matter , 2000 .

[47]  R. Roe,et al.  Methods of X-ray and Neutron Scattering in Polymer Science , 2000 .

[48]  G. Beaucage Small-Angle Scattering from Polymeric Mass Fractals of Arbitrary Mass-Fractal Dimension , 1996 .

[49]  Gregory Beaucage,et al.  Approximations Leading to a Unified Exponential/Power-Law Approach to Small-Angle Scattering , 1995 .

[50]  F. Bates,et al.  Polymer-Polymer Phase Behavior , 1991, Science.

[51]  D. I. Svergun,et al.  Structure Analysis by Small-Angle X-Ray and Neutron Scattering , 1987 .

[52]  O. Glatter Evaluation of small-angle scattering data from lamellar and cylindrical particles by the indirect transformation method , 1980 .

[53]  G. Strobl,et al.  Direct evaluation of the electron density correlation function of partially crystalline polymers , 1980 .

[54]  G. Strobl,et al.  Model of partial crystallization and melting derived from small‐angle X‐ray scattering and electron microscopic studies on low‐density polyethylene , 1980 .

[55]  Otto Glatter,et al.  The interpretation of real-space information from small-angle scattering experiments , 1979 .

[56]  P. F. Peterson,et al.  Mantid 3.4: Manipulation and Analysis Toolkit for Instrument Data. , 2015 .

[57]  P. Adriaensens,et al.  Influence of octanedithiol on the nanomorphology of PCPDTBT:PCBM blends studied by solid-state NMR , 2012 .

[58]  Roar R. Søndergaard,et al.  Advanced materials and processes for polymer solar cell devices , 2010 .

[59]  Leszek A. Utracki,et al.  Polymer Blends Handbook , 2003 .

[60]  Masao Kakudo,et al.  Small Angle Scattering of X-Rays , 1968 .