On the Role of Graphene in Polymer-Based Bulk Heterojunction Solar Cells

Abstract:

As a new material, graphene is considered to have great potential in photovoltaic applications, due to its superior physical and electronic properties. In this manuscript, the behavior of graphene nanosheets prepared by different processing methods were investigated in order to probe their applicability in polymer-based bulk heterojunction optoelectronic devices. Raman spectroscopy was employed to study the formation of interfaces between the conjugated polymer and graphene, while photoluminescence quenching was used to investigate charge transfer from P3HT to graphene. The current-voltage characteristics of fabricated cells were investigated to elucidate the role of graphene in their performance. We demonstrate that the addition of small quantities of graphene promotes exciton dissociation and charge transport in P3HT:PCBM BHJ devices, leading to a novel paradigm for organic solar cells.

• Periodical: Key Engineering Materials (Volume 521)
• Pages: 47-60
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.521.47
• Online since: August 2012
• Authors: Fei Yu, M. Bahner, Vikram K. Kuppa
• Keywords: Bulk Heterojunction, Cell, Graphen, P3HT, PCBM, Polymer, Solar

References

[1] Pope, M. and Swenberg, C. E., Electronic processes in organic crystals and polymers. 2nd ed. Monographs on the physics and chemistry of materials1999, New York: Oxford University Press. xxix, 1328 p.

[2] Siebentritt, S., Gunster, S., and Meissner, D., Junction Effects in Phthalocyanine Thin-Film Solar-Cells. Synth. Met., 1991. 41(3): pp.1173-1176.

DOI: 10.1016/0379-6779(91)91581-t

[3] Tang, C. W., Two-layer organic photovoltaic cell. Appl. Phys. Lett., 1986. 48(2): pp.183-185.

[4] Sariciftci, N. S., et al., Photoinduced Electron-Transfer from a Conducting Polymer to Buckminster fullerene. Science, 1992. 258(5087): pp.1474-1476.

DOI: 10.1126/science.258.5087.1474

[5] Yu, G., et al., Polymer photovoltaic cells: Enhanced efficiencie via a network of internal donor-acceptor heterojunctions. Science, 1995. 270(5243): pp.1789-1791.

DOI: 10.1126/science.270.5243.1789

[6] Hoppe, H. and Sariciftci, N. S., Morphology of polymer/fullerene bulk heterojunction solar cells. J. Mater. Chem., 2006. 16(1): pp.45-61.

DOI: 10.1039/b510618b

[7] Dennler, G., Scharber, M. C., and Brabec, C. J., Polymer-Fullerene Bulk-Heterojunction Solar Cells. Adv. Mater., 2009. 21(13): pp.1323-1338.

DOI: 10.1002/adma.200801283

[8] Hains, A. W., et al., Molecular Semiconductors in Organic Photovoltaic Cells. Chem. Rev., 2010. 110(11): pp.6689-6735.

DOI: 10.1021/cr9002984

[9] Deibel, C. and Dyakonov, V., Polymer-fullerene Bulk Heterojunction Solar Cells. Rep. Prog. Phys., 2010. 73(9): pp.1-39.

DOI: 10.1088/0034-4885/73/9/096401

[10] Vacar, D., et al., Charge-transfer range for photoexcitations in conjugated polymer/fullerene bilayers and blends. Phys. Rev. B, 1997. 56(8): pp.4573-4577.

DOI: 10.1103/physrevb.56.4573

[11] Mihailetchi, V. D., et al., Charge transport and photocurrent generation in poly (3-hexylthiophene): Methanofullerene bulk-heterojunction solar cells. Adv. Funct. Mater., 2006. 16(5): pp.699-708.

DOI: 10.1002/adfm.200500420

[12] Blom, P. W. M., et al., Device physics of polymer : fullerene bulk heterojunction solar cells. Adv. Mater., 2007. 19(12): pp.1551-1566.

DOI: 10.1002/adma.200601093

[13] Kline, R. J., et al., Dependence of regioregular poly(3-hexylthiophene) film morphology and field-effect mobility on molecular weight. Macromolecules, 2005. 38(8): pp.3312-3319.

DOI: 10.1021/ma047415f

[14] Shaheen, S. E., et al., 2. 5% efficient organic plastic solar cells. Appl. Phys. Lett., 2001. 78(6): pp.841-843.

[15] Facchetti, A., et al., Building blocks for N-type molecular and polymeric electronics. Perfluoroalkyl- versus alkyl-functionalized ligothiophenes (nTs; n=2-6). Systematic synthesis, spectroscopy, electrochemistry, and solid-state organization. J. Am. Chem. Soc., 2004. 126(41): pp.13480-13501.

DOI: 10.1021/ja048988a

[16] Hoppe, H., et al., Nanoscale Morphology of Conjugated Polymer/fullerene-based Bulk-heterojunction Solar Cells. Adv. Funct. Mater., 2004. 14(10): pp.1005-1011.

DOI: 10.1002/adfm.200305026

[17] Erb, T., et al., Correlation between structural and optical properties of composite polymer/fullerene films for organic solar cells. Adv. Funct. Mater., 2005. 15(7): pp.1193-1196.

DOI: 10.1002/adfm.200400521

[18] Yang, X. N., et al., Nanoscale morphology of high-performance polymer solar cells. Nano Lett., 2005. 5(4): pp.579-583.

[19] Venkataraman, D., et al., Role of Molecular Architecture in Organic Photovoltaic Cells. J. Phys. Chem. Lett., 2010. 1(6): pp.947-958.

[20] Ma, W. L., et al., Thermally stable, efficient polymer solar cells with nanoscale control of the interpenetrating network morphology. Adv. Funct. Mater., 2005. 15(10): pp.1617-1622.

DOI: 10.1002/adfm.200500211

[21] Lungenschmied, C., et al., Real-time in-situ observation of morphological changes in organic bulk-heterojunction solar cells by means of capacitance measurements. J. Appl. Phys., 2011. 109(4).

DOI: 10.1063/1.3549727

[22] Li, Y., et al., Thermal treatment under reverse bias: Effective tool for polymer/fullerene bulk heterojunction solar cells. Synth. Met., 2008. 158(5): pp.190-193.

DOI: 10.1016/j.synthmet.2007.12.015

[23] Giridharagopal, R. and Ginger, D. S., Characterizing Morphology in Bulk Heterojunction Organic Photovoltaic Systems. J. Phys. Chem. Lett., 2010. 1(7): pp.1160-1169.

DOI: 10.1021/jz100100p

[24] Chen, D. A., et al., P3HT/PCBM Bulk Heterojunction Organic Photovoltaics: Correlating Efficiency and Morphology. Nano Lett., 2011. 11(2): pp.561-567.

DOI: 10.1021/nl103482n

[25] Brabec, C. J., et al., Production aspects of organic photovoltaics and their impact on the commercialization of devices. MRS Bull., 2005. 30(1): pp.50-52.

DOI: 10.1557/mrs2005.10

[26] Kim, Y., et al., Composition and annealing effects in polythiophene/fullerene solar cells. Journal of Materials Science, 2005. 40(6): pp.1371-1376.

[27] Hwang, I. W., Moses, D., and Heeger, A. J., Photoinduced carrier generation in P3HT/PCBM bulk heterojunction materials. J. Phys. Chem. C, 2008. 112(11): pp.4350-4354.

DOI: 10.1021/jp075565x

[28] Huang, Y. C., et al., Quantitative nanoscale monitoring the effect of annealing process on the morphology and optical properties of poly(3-hexylthiophene)/[6, 6]-phenyl C-61-butyric acid methyl ester thin film used in photovoltaic devices. J. Appl. Phys., 2009. 106(3).

DOI: 10.1063/1.3187930

[29] Marsh, R. A., et al., Effect of Annealing on P3HT: PCBM Charge Transfer and Nanoscale Morphology Probed by Ultrafast Spectroscopy. Nano Lett., 2010. 10(3): pp.923-930.

DOI: 10.1021/nl9038289

[30] Howard, I. A., et al., Effect of Morphology on Ultrafast Free Carrier Generation in Polythiophene: Fullerene Organic Solar Cells. J. Am. Chem. Soc., 2010. 132(42): pp.14866-14876.

DOI: 10.1021/ja105260d

[31] Beaujuge, P. M. and Fréchet, J. M. J., Molecular Design and Ordering Effects in π-Functional Materials for Transistor and Solar Cell Applications. J. Am. Chem. Soc., (2011).

DOI: 10.1021/ja2073643

[32] Skotheim, T. A., Elsenbaumer, R. L., and Reynolds, J. R., Handbook of conducting polymers. 2nd ed1998, New York: M. Dekker. xiii, 1097 p.

[33] Morita, S., et al., The Absorption-Spectrum and a Cyclic Voltammogram of C-60-Doped Poly(3-Alkylthiophene). J Phys-Condens Mat, 1993. 5(8): p. L103-L106.

DOI: 10.1088/0953-8984/5/8/001

[34] Facchetti, A., pi-Conjugated Polymers for Organic Electronics and Photovoltaic Cell Applications. Chem. Mat., 2011. 23(3): pp.733-758.

DOI: 10.1021/cm102419z

[35] Mozer, A. J., et al., Charge carrier mobility in regioregular poly(3-hexylthiophene) probed by transient conductivity techniques: A comparative study. Phys. Rev. B, 2005. 71(3).

DOI: 10.1103/physrevb.71.035214

[36] Geim, A. K. and Novoselov, K. S., The rise of graphene. Nat. Mater., 2007. 6(3): pp.183-191.

[37] Novoselov, K. S., et al., Electronic properties of graphene. Phys Status Solidi B, 2007. 244(11): pp.4106-4111.

[38] Liu, Q., et al., Polymer Photovoltaic Cells Based on Solution-Processable Graphene and P3HT. Adv. Funct. Mater., 2009. 19(6): pp.894-904.

DOI: 10.1002/adfm.200800954

[39] Yang, Z. L., et al., Preparation of poly(3-hexylthiophene)/graphene nanocomposite via in situ reduction of modified graphite oxide sheets. Appl Surf Sci, 2010. 257(1): pp.138-142.

DOI: 10.1016/j.apsusc.2010.06.051

[40] Li, S. S., et al., Solution-Processable Graphene Oxide as an Efficient Hole Transport Layer in Polymer Solar Cells. ACS Nano, 2010. 4(6): pp.3169-3174.

DOI: 10.1021/nn100551j

[41] Hill, C. M., Zhu, Y., and Pan, S., Fluorescence and Electroluminescence Quenching Evidence of Interfacial Charge Transfer in Poly (3-hexylthiophene): Graphene Oxide Bulk Heterojunction Photovoltaic Devices. ACS Nano, 2011. 5(2): pp.942-951.

DOI: 10.1021/nn1022457

[42] Yu, D., et al., Soluble P3HT-Grafted Graphene for Efficient Bilayer−Heterojunction Photovoltaic Devices. ACS Nano, 2010. 4(10): pp.5633-5640.

DOI: 10.1021/nn101671t

[43] Yu, D. S., et al., Fullerene-Grafted Graphene for Efficient Bulk Heterojunction Polymer Photovoltaic Devices. J. Phys. Chem. Lett., 2011. 2(10): pp.1113-1118.

DOI: 10.1021/jz200428y

[44] Gus'kova, O. A., et al., Self-assembled monolayers of beta-alkylated oligothiophenes on graphite substrate: Molecular dynamics simulation. J. Phys. Chem. C, 2007. 111(19): pp.7165-7174.

DOI: 10.1021/jp0704618

[45] Surin, M., et al., Molecule-molecule versus molecule-substrate interactions in the assembly of oligothiophenes at surfaces. J. Phys. Chem. B, 2006. 110(15): pp.7898-7908.

DOI: 10.1021/jp056824q

[46] Wang, Y. B., et al., Fluorescence Quenching in Conjugated Polymers Blended with Reduced Graphitic Oxide. J. Phys. Chem. C, 2010. 114(9): pp.4153-4159.

DOI: 10.1021/jp9097793

[47] Yu, Y. -J., et al., Tuning the Graphene Work Function by Electric Field Effect. Nano Lett., 2009. 9(10): pp.3430-3434.

DOI: 10.1021/nl901572a

[48] Kudin, K. et al., Raman Spectra of Graphite Oxide and Functionalized Graphene Sheets. Nano Lett. 2008. 8: pp.36-41.

[49] Rao, A. M., et al., Evidence for charge transfer in doped carbon nanotube bundles from Raman scattering. Nature, 1997. 388(6639): pp.257-259.

DOI: 10.1038/40827

[50] Su, Q., et al., Composites of Graphene with Large Aromatic Molecules. Adv. Mater., 2009. 21(31): p.3191.

[51] Yu, F. and Kuppa, V.K. The performance of P3HT: PCBM solar cells with pristine graphene. Appl. Phys. Lett. (submitted).

[52] Kymakis, E., Kornilios, N. and Koudoumas, E. Carbon nanotube doping of P3HT : PCBM photovoltaic devices. J. Phys. D. Appl. Phys., 2008. 41: p.165110.

DOI: 10.1088/0022-3727/41/16/165110