Skip to main content
Log in

Theoretical description of the geometric and electronic structures of organic-organic interfaces in organic solar cells: a brief review

  • Feature Articles
  • Special Issue Quantum Chemistry for Extended Systems—In honor of Prof. J.M. André for his 70th birthday
  • Published:
Science China Chemistry Aims and scope Submit manuscript

Abstract

We review some of the computational methodologies used in our research group to develop a better understanding of the geometric and electronic structures of organic-organic interfaces present in the active layer of organic solar cells. We focus in particular on the exciton-dissociation and charge-transfer processes at the pentacene-fullerene interface. We also discuss the local morphology at this interface on the basis of molecular dynamics simulations.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Similar content being viewed by others

References

  1. Morel DL, Ghosh AK, Feng T, Stogryn EL, Purwin PE, Shaw RF, Fishman C. High-efficiency organic solar cells. Appl Phys Lett, 1978, 32: 495–497

    Article  CAS  Google Scholar 

  2. Tang CW. Two-layer organic photovoltaic cell. Appl Phys Lett, 1986, 48: 183–185

    Article  CAS  Google Scholar 

  3. Hiramoto M, Fujiwara H, Yokoyama M. Three-layered organic solar cell with a photoactive interlayer of codeposited pigments. Appl Phys Lett, 1991, 58: 1062–1064

    Article  CAS  Google Scholar 

  4. Halls JJM, Walsh CA, Greenham NC, Marseglia EA, Friend RH, Moratti SC, Holmes AB. Efficient photodiodes from interpenetrating polymer networks. Nature, 1995, 376: 498–500

    Article  CAS  Google Scholar 

  5. Yu G, Gao J, Hummelen JC, Wudl F, Heeger AJ. Polymer photovoltaic cells: enhanced efficiencies via a network of internal donor-acceptor heterojunctions. Science, 1995, 270: 1789–1791

    Article  CAS  Google Scholar 

  6. Risko C, McGehee MD, Bredas JL. A quantum-chemical perspective into low optical-gap polymers for highly-efficient organic solar cells. Chem Sci, 2011, 2: 1200–1218

    Article  CAS  Google Scholar 

  7. Potscavage WJ, Sharma A, Kippelen B. Critical interfaces in organic solar cells and their influence on the open-circuit voltage. Acc Chem Res, 2009, 42: 1758–1767

    Article  CAS  Google Scholar 

  8. Anthony JE, Facchetti A, Heeney M, Marder SR, Zhan X. N-type organic semiconductors in organic electronics. Adv Mater, 2010, 22: 3876–3892

    Article  CAS  Google Scholar 

  9. Kippelen B, Bredas JL. Organic photovoltaics. Energy Environ Sci, 2009, 2: 251–261

    Article  CAS  Google Scholar 

  10. Bredas JL, Norton JE, Cornil J, Coropceanu V. Molecular understanding of organic solar cells: the challenges. Acc Chem Res, 2009, 42: 1691–1699

    Article  CAS  Google Scholar 

  11. Hoppe H, Sariciftci NS. Organic solar cells: an overview. J Mater Res, 2004, 19: 1924–1945

    Article  CAS  Google Scholar 

  12. Thompson BC, Fréchet JMJ. Polymer-fullerene composite solar cells. Angew Chem Int Ed, 2008, 47: 58–77

    Article  CAS  Google Scholar 

  13. Bredas JL, Street GB. Polarons, bipolarons, and solitons in conducting polymers. Acc Chem Res, 1985, 18: 309–315

    Article  CAS  Google Scholar 

  14. Banerji N, Cowan S, Leclerc M, Vauthey E, Heeger AJ. Exciton formation, relaxation, and decay in PCDTBT. J Am Chem Soc, 2010, 132: 17459–17470

    Article  CAS  Google Scholar 

  15. Gélinas S, Rao A, Kumar A, Smith SL, Chin AW, Clark J, van der Poll TS, Bazan GC, Friend RH. Ultrafast long-range charge separation in organic semiconductor photovoltaic diodes. Science, 2014, 343: 512–516

    Article  Google Scholar 

  16. Bredas JL. When electrons leave holes in organic solar cells. Science, 2014, 343: 492–493

    Article  CAS  Google Scholar 

  17. Potscavage WJ, Yoo S, Kippelen B. Origin of the open-circuit voltage in multilayer heterojunction organic solar cells. Appl Phys Lett, 2008, 93: 193308

    Article  Google Scholar 

  18. Perez MD, Borek C, Forrest SR, Thompson ME. Molecular and morphological influences on the open circuit voltages of organic photovoltaic devices. J Am Chem Soc, 2009, 131: 9281–9286

    Article  CAS  Google Scholar 

  19. Kawatsu T, Coropceanu V, Ye A, Bredas JL. Quantum-chemical approach to electronic coupling: application to charge separation and charge recombination pathways in a model molecular donor-acceptor system for organic solar cells. J Phys Chem C, 2008, 112: 3429–3433

    Article  CAS  Google Scholar 

  20. Yi Y, Coropceanu V, Bredas JL. Exciton-dissociation and charge-recombination processes in pentacene/C60 solar cells: theoretical insight into the impact of interface geometry. J Am Chem Soc, 2009, 131: 15777–15783

    Article  CAS  Google Scholar 

  21. Edmonds AR. Angular Momentum in Quantum Mechanics. Princeton: Princeton University Press, 1985

    Google Scholar 

  22. Ridley J, Zerner M. Intermediate neglect of differential overlap technique for spectroscopy: pyrrole and azines. Theor Chim Acta, 1973, 32: 111–134

    Article  CAS  Google Scholar 

  23. Marcus RA. Electron transfer reactions in chemistry. Theory and experiment. Rev Mod Phys, 1993, 65: 599–610

    Article  CAS  Google Scholar 

  24. Barbara PF, Meyer TJ, Ratner MA. Contemporary issues in electron transfer research. J Phys Chem, 1996, 100: 13148–13168

    Article  CAS  Google Scholar 

  25. Akimoto I, Ashida M, Kan’no K. Luminescence from C60 single crystals in glassy phase under site-selective excitation. Chem Phys Lett, 1998, 292: 561–566

    Article  CAS  Google Scholar 

  26. Jundt C, Klein G, Sipp B, Lemoigne J, Joucla M, Villaeys AA. Exciton dynamics in pentacene thin-films studied by pump-probe spectroscopy. Chem Phys Lett, 1995, 241: 84–88

    Article  CAS  Google Scholar 

  27. Faltermeier D, Gompf B, Dressel M, Tripathi AK, Pflaum J. Optical properties of pentacene thin films and single crystals. Phys Rev B, 2006, 74: 125416

    Article  Google Scholar 

  28. Hwang J, Wan A, Kahn A. Energetics of metal-organic interfaces: new experiments and assessment of the field. Mat Sci Eng R, 2009, 64: 1–31

    Article  Google Scholar 

  29. Schwedhelm R, Kipp L, Dallmeyer A, Skibowski M. Experimental band gap and core-hole electron interaction in epitaxial C60 films. Phys Rev B, 1998, 58: 13176–13180

    Article  CAS  Google Scholar 

  30. Kato T, Kodama T, Shida T, Nakagawa T, Matsui Y, Suzuki S, Shiromaru H, Yamauchi K, Achiba Y. Electronic absorption spectra of the radical anions and cations of fullerenes: C60 and C70. Chem Phys Lett, 1991, 180: 446–450

    Article  CAS  Google Scholar 

  31. Kato T, Kodama T, Shida T. Spectroscopic studies of the radical anion of C60. Detection of the fluorenscence and reinvestigation of the ESR spectrum. Chem Phys Lett, 1993, 205: 405–409

    Article  CAS  Google Scholar 

  32. Szczepanski J, Wehlburg C, Vala M. Vibrational and electronic-spectra of matrix-isolated pentacene cations and anions. Chem Phys Lett, 1995, 232: 221–228

    Article  CAS  Google Scholar 

  33. Rand BP, Cheyns D, Vasseur K, Giebink NC, Mothy S, Yi YP, Coropceanu V, Beljonne D, Cornil J, Bredas JL, Genoe J. The impact of molecular orientation on the photovoltaic properties of a phthalocyanine/fullerene heterojunction. Adv Funct Mater, 2012, 22: 2987–2995

    Article  CAS  Google Scholar 

  34. Campoy-Quiles M, Ferenczi T, Agostinelli T, Etchegoin PG, Kim Y, Anthopoulos TD, Stavrinou PN, Bradley DDC, Nelson J. Morphology evolution via self-organization and lateral and vertical diffusion in polymer: fullerene solar cell blends. Nat Mater, 2008, 7: 158–164

    Article  CAS  Google Scholar 

  35. Mayer AC, Toney MF, Scully SR, Rivnay J, Brabec CJ, Scharber M, Koppe M, Heeney M, McCulloch I, McGehee MD. Bimolecular crystals of fullerenes in conjugated polymers and the implications of molecular mixing for solar cells. Adv Funct Mater, 2009, 19: 1173–1179

    Article  CAS  Google Scholar 

  36. Collins BA, Gann E, Guignard L, He X, McNeill CR, Ade H. Molecular miscibility of polymer-fullerene blends. J Phys Chem Lett, 2010, 1: 3160–3166

    Article  CAS  Google Scholar 

  37. Chen D, Nakahara A, Wei D, Nordlund D, Russell TP. P3HT/PCBM bulk heterojunction organic photovoltaics: correlating efficiency and morphology. Nano Lett, 2010, 11: 561–567

    Article  Google Scholar 

  38. Szarko JM, Guo J, Liang Y, Lee B, Rolczynski BS, Strzalka J, Xu T, Loser S, Marks TJ, Yu L, Chen LX. When function follows form: effects of donor copolymer side chains on film morphology and BHJ solar cell performance. Adv Mater, 2010, 22: 5468–5472

    Article  CAS  Google Scholar 

  39. Yin W, Dadmun M. A new model for the morphology of P3HT/PCBM organic photovoltaics from small-angle neutron scattering: rivers and streams. Acs Nano, 2011, 5: 4756–4768

    Article  CAS  Google Scholar 

  40. Lu H, Akgun B, Russell TP. Morphological characterization of a low-bandgap crystalline polymer: PCBM bulk heterojunction solar cells. Adv Energy Mater, 2011, 1: 870–878

    Article  CAS  Google Scholar 

  41. Parnell AJ, Cadby AJ, Mykhaylyk OO, Dunbar ADF, Hopkinson PE, Donald AM, Jones RAL. Nanoscale phase separation of P3HTPCBM thick films as measured by small-angle X-ray scattering. Macromolecules, 2011, 44: 6503–6508

    Article  CAS  Google Scholar 

  42. Collins BA, Tumbleston JR, Ade H. Miscibility, crystallinity, and phase development in P3HT/PCBM solar cells: toward an enlightened understanding of device morphology and stability. J Phys Chem Lett, 2011, 2: 3135–3145

    Article  CAS  Google Scholar 

  43. Jamieson FC, Domingo EB, McCarthy-Ward T, Heeney M, Stingelin N, Durrant JR. Fullerene crystallisation as a key driver of charge separation in polymer/fullerene bulk heterojunction solar cells. Chem Sci, 2012, 3: 485–492

    Article  CAS  Google Scholar 

  44. Miller NC, Sweetnam S, Hoke ET, Gysel R, Miller CE, Bartelt JA, Xie X, Toney MF, McGehee MD. Molecular packing and solar cell performance in blends of polymers with a bisadduct fullerene. Nano Lett, 2012, 12: 1566–1570

    Article  CAS  Google Scholar 

  45. Treat ND, Brady MA, Smith G, Toney MF, Kramer EJ, Hawker CJ, Chabinyc ML. Interdiffusion of PCBM and P3HT reveals miscibility in a photovoltaically active blend. Adv Energy Mater, 2011, 1: 82–89

    Article  CAS  Google Scholar 

  46. Sai N, Gearba R, Dolocan A, Tritsch JR, Chan WL, Chelikowsky JR, Leung K, Zhu X. Understanding the interface dipole of copper phthalocyanine (CuPc)/C60: theory and experiment. J Phys Chem Lett, 2012, 3: 2173–2177

    Article  CAS  Google Scholar 

  47. Loiudice A, Rizzo A, Biasiucci M, Gigli G. Bulk heterojunction versus diffused bilayer: the role of device geometry in solution p-doped polymer-based solar cells. J Phys Chem Lett, 2012, 3: 1908–1915

    Article  CAS  Google Scholar 

  48. Loiudice A, Rizzo A, Latini G, Nobile C, de Giorgi M, Gigli G. Graded vertical phase separation of donor/acceptor species for polymer solar cells. Sol Energ Mat Sol C, 2012, 100: 147–152

    Article  CAS  Google Scholar 

  49. Poschlad A, Meded V, Maul R, Wenzel W. Different interface orientations of pentacene and PTCDA induce different degrees of disorder. Nanoscale Res Lett, 2012, 7: 248

    Article  Google Scholar 

  50. Brabec CJ, Durrant JR. Solution-processed organic solar cells. Mrs Bull, 2008, 33: 670–675

    Article  CAS  Google Scholar 

  51. Helgesen M, Sondergaard R, Krebs FC. Advanced materials and processes for polymer solar cell devices. J Mater Chem, 2010, 20: 36–60

    Article  CAS  Google Scholar 

  52. Krebs FC. Fabrication and processing of polymer solar cells: a review of printing and coating techniques. Sol Energ Mat Sol C, 2009, 93: 394–412

    Article  CAS  Google Scholar 

  53. Lyons BP, Clarke N, Groves C. The relative importance of domain size, domain purity and domain interfaces to the performance of bulk-heterojunction organic photovoltaics. Energy Environ Sci, 2012, 5: 7657–7663

    Article  CAS  Google Scholar 

  54. Yoo S, Domercq B, Kippelen B. Efficient thin-film organic solar cells based on pentacene/C60 heterojunctions. Appl Phys Lett, 2004, 85: 5427–5429

    Article  CAS  Google Scholar 

  55. Pandey AK, Nunzi JM. Efficient flexible and thermally stable pentacene/C60 small molecule based organic solar cells. Appl Phys Lett, 2006, 89: 213506

    Article  Google Scholar 

  56. Yang YC, Chang CH, Lee YL. Complexation of fullerenes on a pentacene-modified Au(111) surface. Chem Mater, 2007, 19: 6126–6130

    Article  CAS  Google Scholar 

  57. Al-Mahboob A, Sadowski JT, Fujikawa Y, Nakajima K, Sakurai T. Kinetics-driven anisotropic growth of pentacene thin films. Phys Rev B, 2008, 77: 035426

    Article  Google Scholar 

  58. Dougherty DB, Jin W, Cullen WG, Dutton G, Reutt-Robey JE, Robey SW. Local transport gap in C60 nanochains on a pentacene template. Phys Rev B, 2008, 77: 073414

    Article  Google Scholar 

  59. Conrad BR, Tosado J, Dutton G, Dougherty DB, Jin W, Bonnen T, Schuldenfrei A, Cullen WG, Williams ED, Reutt-Robey JE, Robey SW. C60 cluster formation at interfaces with pentacene thin-film phases. Appl Phys Lett, 2009, 95: 213302

    Article  Google Scholar 

  60. Dougherty DB, Jin W, Cullen WG, Reutt-Robey JE, Robey SW. Striped domains at the pentacene: C60 interface. Appl Phys Lett, 2009, 94: 023103

    Article  Google Scholar 

  61. Jin W, Dougherty DB, Cullen WG, Robey S, Reutt-Robey JE. C60-pentacene network formation by 2-d co-crystallization. Langmuir, 2009, 25: 9857–9862

    Article  CAS  Google Scholar 

  62. Cantrell R, Clancy P. A computational study of surface diffusion of C60 on pentacene. Surf Sci, 2008, 602: 3499–3505

    Article  CAS  Google Scholar 

  63. Verlaak S, Beljonne D, Cheyns D, Rolin C, Linares M, Castet F, Cornil J, Heremans P. Electronic structure and geminate pair energetics at organic-organic interfaces: the case of pentacene/C60 heterojunctions. Adv Funct Mater, 2009, 19: 3809–3814

    Article  CAS  Google Scholar 

  64. Zheng Y, Pregler SK, Myers JD, Ouyang JM, Sinnott SB, Xue JG. Computational and experimental studies of phase separation in pentacene:C60 mixtures. J Vac Sci Technol B, 2009, 27: 169–179

    Article  CAS  Google Scholar 

  65. Cantrell R, Clancy P. A molecular dynamics study of the effect of pentacene polymorphs on C60 surface adsorption and diffusional properties and the tendency to form nanowires. Mol Simulat, 2010, 36: 590–603

    Article  CAS  Google Scholar 

  66. Linares M, Beljonne D, Cornil J, Lancaster K, Bredas JL, Verlaak S, Mityashin A, Heremans P, Fuchs A, Lennartz C, Ide J, Mereau R, Aurel P, Ducasse L, Castet F. On the interface dipole at the pentacene-fullerene heterojunction: a theoretical study. J Phys Chem C, 2010, 114: 3215–3224

    Article  CAS  Google Scholar 

  67. Cantrell RA, James C, Clancy P. Computationally derived rules for persistence of C60 nanowires on recumbent pentacene bilayers. Langmuir, 2011, 27: 9944–9954

    Article  CAS  Google Scholar 

  68. Minami T, Nakano M, Castet Fdr. Nonempirically tuned long-range corrected density functional theory study on local and charge-transfer excitation energies in a pentacene/C60 model complex. J Phys Chem Lett, 2011, 2: 1725–1730

    Article  CAS  Google Scholar 

  69. Muccioli L, D’Avino G, Zannoni C. Simulation of vapor-phase deposition and growth of a pentacene thin film on C60 (001). Adv Mater, 2011, 23: 4532–4536

    Article  CAS  Google Scholar 

  70. Lii JH, Allinger NL. Molecular mechanics. The MM3 force field for hydrocarbons. 3. The van der Waals’ potentials and crystal data for aliphatic and aromatic hydrocarbons. J Am Chem Soc, 1989, 111: 8576–8582

    Article  CAS  Google Scholar 

  71. Fu YT, Risko C, Bredas JL. Intermixing at the pentacene-fullerene bilayer interface: a molecular dynamics study. Adv Mater, 2013, 25: 878–882

    Article  CAS  Google Scholar 

  72. Drummy LF, Miska PK, Alberts D, Lee N, Martin DC. Imaging of crystal morphology and molecular simulations of surface energies in pentacene thin films. J Phys Chem B, 2006, 110: 6066–6071

    Article  CAS  Google Scholar 

  73. Cheng HL, Lin JW. Controlling polymorphic transformations of pentacene crystal through solvent treatments: an experimental and theoretical study. Cryst Growth Des, 2010, 10: 4501–4508

    Article  CAS  Google Scholar 

  74. Desai TV, Woll AR, Engstrom JR. Thin film growth of pentacene on polymeric dielectrics: unexpected changes in the evolution of surface morphology with substrate. J Phys Chem C, 2012, 116: 12541–12552

    Article  CAS  Google Scholar 

  75. Ruiz R, Choudhary D, Nickel B, Toccoli T, Chang KC, Mayer AC, Clancy P, Blakely JM, Headrick RL, Iannotta S, Malliaras GG. Pentacene thin film growth. Chem Mater, 2004, 16: 4497–4508

    Article  CAS  Google Scholar 

  76. Northrup JE, Tiago ML, Louie SG. Surface energetics and growth of pentacene. Phys Rev B, 2002, 66: 121404

    Article  Google Scholar 

  77. Drummy LF, Martin DC. Thickness-driven orthorhombic to triclinic phase transformation in pentacene thin films. Adv Mater, 2005, 17: 903–907

    Article  CAS  Google Scholar 

  78. Feng M, Lee J, Zhao J, Yates JT Jr, Petek H. Nanoscale templating of close-packed C60 nanowires. J Am Chem Soc, 2007, 129: 12394–12395

    Article  CAS  Google Scholar 

  79. Guo YJ, Karasawa N, Goddard WA. Prediction of fullerene packing in C60 and C70 crystals. Nature, 1991, 351: 464–467

    Article  CAS  Google Scholar 

  80. Ma X, Wigington B, Bouchard D. Fullerene C60: surface energy and interfacial interactions in aqueous systems. Langmuir, 2010, 26: 11886–11893

    Article  CAS  Google Scholar 

  81. Neel N, Kroger J, Berndt R. Highly periodic fullerene nanomesh. Adv Mater, 2006, 18: 174–177

    Article  CAS  Google Scholar 

  82. Pawlak R, Kawai S, Fremy S, Glatzel T, Meyer E. Atomic-scale mechanical properties of orientated C60 molecules revealed by noncontact atomic force microscopy. Acs Nano, 2011, 5: 6349–6354

    Article  CAS  Google Scholar 

  83. Xiao WD, Ruffieux P, Ait-Mansour K, Groning O, Palotas K, Hofer WA, Groning P, Fasel R. Formation of a regular fullerene nanochain lattice. J Phys Chem B, 2006, 110: 21394–21398

    Article  CAS  Google Scholar 

  84. Zhang HL, Chen W, Huang H, Chen L, Wee AT. Preferential trapping of C60 in nanomesh voids. J Am Chem Soc, 2008, 130: 2720–2721

    Article  CAS  Google Scholar 

  85. Zimmerman JD, Xiao X, Renshaw CK, Wang S, Diev VV, Thompson ME, Forrest SR. Independent control of bulk and interfacial morphologies of small molecular weight organic heterojunction solar cells. Nano Lett, 2012, 12: 4366–4371

    Article  CAS  Google Scholar 

  86. McMahon DP, Cheung DL, Troisi A. Why holes and electrons separate so well in polymer/fullerene photovoltaic cells. J Phys Chem Lett, 2011, 2: 2737–2741

    Article  CAS  Google Scholar 

  87. Körzdörfer T, Sears JS, Sutton C, Bredas JL. Long-range corrected hybrid functionals for pi-conjugated systems: dependence of the range-separation parameter on conjugation length. J Chem Phys, 2011, 135: 204107

    Article  Google Scholar 

  88. Pandey L, Doiron C, Sears JS, Bredas JL. Lowest excited states and optical absorption spectra of donor-acceptor copolymers for organic photovoltaics: a new picture emerging from tuned long-range corrected density functionals. Phys Chem Chem Phys, 2012, 14: 14243–14248

    Article  CAS  Google Scholar 

  89. Körzdörfer T, Parrish RM, Sears JS, Sherrill CD, Bredas JL. On the relationship between bond-length alternation and many-electron self-interaction error. J Chem Phys, 2012, 137: 124305

    Article  Google Scholar 

  90. Körzdörfer T, Parrish RM, Marom N, Sears JS, Sherrill CD, Brédas JL. Assessment of the performance of tuned range-separated hybrid density functionals in predicting accurate quasiparticle spectra. Phys Rev B, 2012, 86: 205110

    Article  Google Scholar 

  91. Grimm B, Risko C, Azoulay JD, Bredas JL, Bazan GC. Structural dependence of the optical properties of narrow bandgap semi-conductors with orthogonal donor-acceptor geometries. Chem Sci, 2013, 4: 1807–1819

    Article  CAS  Google Scholar 

  92. Zhang CR, Coropceanu V, Sears JS, Bredas JL. Vibronic coupling in the ground state of oligoacene cations: the performance of range-separated hybrid density functionals. J Phys Chem C, 2014, 118: 154–158

    Article  CAS  Google Scholar 

  93. Ryno SM, Lee SR, Sears JS, Risko C, Brédas JL. Electronic polarization effects upon charge injection in oligoacene molecular crystals: description via a polarizable force field. J Phys Chem C, 2013, 117: 13853–13860

    Article  CAS  Google Scholar 

  94. Ryno SM, Risko C, Bredas JL. Impact of molecular packing on electronic polarization in organic crystals: the case of pentacene vs tips-pentacene. J Am Chem Soc, 2014, 136: 6421–6427

    Article  CAS  Google Scholar 

  95. Burke TM, McGehee MD. How high local charge carrier mobility and an energy cascade in a three-phase bulk heterojunction enable > 90% quantum efficiency. Adv Mater, 2014, 26: 1923–1928

    Article  CAS  Google Scholar 

Download references

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Jean-Luc Brédas.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Fu, YT., Yi, Y., Coropceanu, V. et al. Theoretical description of the geometric and electronic structures of organic-organic interfaces in organic solar cells: a brief review. Sci. China Chem. 57, 1330–1339 (2014). https://doi.org/10.1007/s11426-014-5184-x

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s11426-014-5184-x

Keywords

Navigation