Polymer solar cell
||It has been suggested that this article be merged with Organic solar cell. (Discuss) Proposed since March 2014.|
A polymer solar cell is a type of flexible solar cell made with polymers, large molecules with repeating structural units, that produce electricity from sunlight by the photovoltaic effect. Polymer solar cells include organic solar cells (also called "plastic solar cells"). They are one type of thin film solar cell, others include the more stable amorphous silicon solar cell.
Most commercial solar cells are made from a refined, highly purified silicon crystal, similar to the material used in the manufacture of integrated circuits and computer chips (wafer silicon). The high cost of these silicon solar cells and their complex production process generated interest in alternative technologies.
Compared to silicon-based devices, polymer solar cells are lightweight (which is important for small autonomous sensors), potentially disposable and inexpensive to fabricate (sometimes using printed electronics), flexible, customizable on the molecular level and potentially have smaller negative environmental impact. An example device is shown in Fig. 1. The disadvantages of polymer solar cells are also serious: they offer about 1/3 of the efficiency of hard materials, and are experience substantial photochemical degradation.
Polymer solar cells inefficiency and stability problems, combined with their promise of low costs and increased efficiency made them a popular field in solar cell research. As of 2014 laboratory devices had reached certified efficiencies above 8%, while as yet unpublished devices exceeded 10%.
Polymer solar cells usually consist of an electron- or hole-blocking layer on top of an indium tin oxide (ITO) conductive glass followed by electron donor and an electron acceptor (in the case of bulk heterojunction solar cells), a hole or electron blocking layer, and metal electrode on top. The nature and order of the blocking layers – as well as the nature of the metal electrode – depends on whether the cell follows a regular or an inverted device architecture.
In bulk heterojunction polymer solar cells, light generates excitons. Subsequent charge separation in the interface between an electron donor and acceptor blend within the device’s active layer. These charges then transport to the device’s electrodes where the charges flow outside the cell, perform work and then re-enter the device on the opposite side. The cell's efficiency is limited by several factors, especially non-geminate recombination. Hole mobility leads to faster conduction across the active layer.
Organic photovoltaics are made of electron donor and electron acceptor materials rather than semiconductor p-n junctions. The molecules forming the electron donor region of organic PV cells, where exciton electron-hole pairs are generated, are generally conjugated polymers possessing delocalized π electrons that result from carbon p orbital hybridization. These π electrons can be excited by light in or near the visible part of the spectrum from the molecule's highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO), denoted by a π -π* transition. The energy bandgap between these orbitals determines which wavelength(s) of light can be absorbed.
Unlike in an inorganic crystalline PV cell material, with its band structure and delocalized electrons, excitons in organic photovoltaics are strongly bound with an energy between 0.1 and 1.4 eV. This strong binding occurs because electronic wave functions in organic molecules are more localized, and electrostatic attraction can thus keep the electron and hole together as an exciton. The electron and hole can be dissociated by providing an interface across which the chemical potential of electrons decreases. The material that absorbs the photon is the donor, and the material acquiring the electron is called the acceptor. In Fig. 2, the polymer chain is the donor and the fullerene is the acceptor. Even after dissociation, the electron and hole may still be joined as a "geminate pair", and an electric field is then required to separate them. The electron and hole must be collected at contacts. If charge carrier mobility is insufficient, the carriers will not reach the contacts, and instead recombine at trap sites or remain in the device as undesirable space charges that oppose the flow of new carriers. The latter problem can occur if electron and hole mobilities are not matched. In that case, space-charge limited photocurrent (SCLP) hampers device performance.
Organic photovoltaics can be fabricated with an active polymer and a fullerene-based electron acceptor. Illumination of this system by visible light leads to electron transfer from the polymer to a fullerene molecule. As a result, the formation of a photoinduced quasiparticle, or polaron (P+), occurs on the polymer chain and the fullerene becomes a radical anion (C−
60). Polarons are highly mobile and can diffuse away.
The simplest organic PV device features a planar heterojunction (figure 1). A film of active polymer (donor) and a film of electron acceptor is sandwiched between contacts. Excitons created in the donor region may diffuse to the junction and separate, with the hole remaining behind and the electron passing into the acceptor. Because charge carriers have diffusion lengths of just 3–10 nm in typical organic semiconductors, planar cells must be thin, but the thin cells absorb light less well. Bulk heterojunctions (BHJs) address this shortcoming. In a BHJ, a blend of electron donor and acceptor materials is cast as a mixture, which then phase-separates. Regions of each material in the device are separated by only several nanometers, a distance suited for carrier diffusion. BHJs require sensitive control over materials morphology on the nanoscale. Important variables include materials, solvents and the donor-acceptor weight ratio.
The next logical step beyond BHJs are ordered nanomaterials for solar cells, or ordered heterojunctions (OHJs). OHJs minimize the variability associated with BHJs. OHJs are generally hybrids of ordered inorganic materials and organic active regions. For example, a photovoltaic polymer can be deposited into pores in a ceramic such as TiO2. Since holes still must diffuse the length of the pore through the polymer to a contact, OHJs suffer similar thickness limitations. Mitigating the hole mobility bottleneck is key to further enhancing device performance of OHJ's.
Active layer deposition and annealing process
Since its active layer largely determines device efficiency, this component's morphology received much attention.
If one material is more soluble in the solvent than the other, it will deposit first on top of the substrate, causing a concentration gradient through the film. This has been demonstrated for poly-3-hexyl thiophene (P3HT), phenyl-C61-butyric acid methyl ester (PCBM) devices where the PCBM tends to accumulate towards the device's bottom upon spin coating from ODCB solutions. This effect is seen because the more soluble component tends to migrate towards the “solvent rich” phase during the coating procedure, accumulating the more soluble component towards the film's bottom, where the solvent remains longer. The thickness of the generated film affects the phases segregation because the dynamics of crystallization and precipitation are different for more concentrated solutions or faster evaporation rates (needed to build thicker devices). Crystalline P3HT enrichment closer to the hole-collecting electrode can only be achieved for relatively thin (100 nm) P3HT/PCBM layers.
The gradients in the initial morphology are then mainly generated by the solvent evaporation rate and the differences in solubility between the donor and acceptor inside the blend. This dependence on solubility has been clearly demonstrated using fullerene derivatives and P3HT. When using solvents which evaporate at a slower rate (as chlorobenzene (CB) or dichlorobenzene (DCB)) you can get larger degrees of vertical separation or aggregation while solvents that evaporate quicker produce a much less effective vertical separation. Larger solubility gradients should lead to more effective vertical separation while smaller gradients should lead to more homogeneous films. These two effects were verified on P3HT:PCBM solar cells.
The solvent evaporation speed as well as posterior solvent vapor or thermal annealing procedures were also studied. Blends such as P3HT:PCBM seem to benefit from thermal annealing procedures, while others, such as PTB7:PCBM, seem to show no benefit. In P3HT the benefit seems to come from an increase of crystallinity of the P3HT phase which is generated through an expulsion of PCBM molecules from within these domains. This has been demonstrated through studies of PCBM miscibility in P3HT as well as domain composition changes as a function of annealing times.
The above hypothesis based on miscibility does not fully explain the efficiency of the devices as solely pure amorphous phases of either donor or acceptor materials never exist within bulk heterojunction devices. A 2010 paper suggested that current models that assume pure phases and discrete interfaces might fail given the absence of pure amorphous regions. Since current models assume phase separation at interfaces without any consideration for phase purity, the models might need to be changed.
The thermal annealing procedure varies depending on precisely when it is applied. Since vertical species migration is partly determined by the surface tension between the active layer and either air or another layer, annealing before or after the deposition of additional layers (most often the metal cathode) affects the result. In the case of P3HT:PCBM solar cells vertical migration is improved when cells are annealed after the deposition of the metal cathode.
Donor or acceptor accumulation next to the adjacent layers might be beneficial as these accumulations can lead to hole or electron blocking effects which might benefit device performance. In 2009 the difference in vertical distribution on P3HT:PCBM solar cells was shown to cause problems with electron mobility which ends up with the yielding of very poor device efficiencies. Simple changes to device architecture – spin coating a thin layer of PCBM on top of the P3HT – greatly enhance cell reproducibility, by providing reproducible vertical separation between device components. Since higher contact between the PCBM and the cathode is required for better efficiencies, this largely increases device reproducibility.
According to neutron scattering analysis, P3HT:PCBM blends have been described as “rivers" (P3HT" interrupted by “streams” (PCBM regions).
Conditions for spin coating and evaporation affect device efficiency. Solvent and additives influence donor-acceptor morphology. Additives slow down evaporation, leading to more crystalline polymers and thus improved hole conductivities and efficiencies. Typical additives include 1,8-octanedithiol, ortho-dichlorobenzene, 1,8-diiodooctane (DIO), and nitrobenzene. The DIO effect was attributed to the selective solubilization of the PCBM component. Additives can also lead to big increases in efficiency for polymers. For HXS-1/PCBM solar cells, the effect was correlated with charge generation, transport and shelf-stability. Other polymers such as PTTBO also benefit significantly from DIO, achieving PCE values of more than 5% from around 3.7% without the additive.
Small differences in polymer structure can also lead to significant changes in crystal packing that inevitably affect device morphology. PCPDTBT differs from PSBTBT caused by the difference in bridging atom between the two polymers (C vs. Si), which implies that better morphologies are achievable with PCPDTBT:PCBM solar cells containing additives as opposed to the Si system which achieves good morphologies without help from additional substances.
Supramolecular chemistry was investigated, using donor and acceptor molecules that assemble upon spin casting and heating. Most supramolecular assemblies employ small molecules. Donor and acceptor domains in a tubular structure appear ideal for organic solar cells.
Diblock polymers containing fullerene yield stable organic solar cells upon thermal annealing. Solar cells with pre-designed morphologies resulted when appropriate supramolecular interactions are introduced.
Device efficiency based on co-polymer approaches have yet to cross the 2% barrier, whereas bulk-heterojunction devices exhibit efficiencies >7% in single junction configurations.
Supramolecular approaches to organic solar cells provide understanding about the macromolecular forces that drive domain separation.
Infrared polymer cells
Infrared cells preferentially absorb light in the infrared range rather than visible wavelengths. As of 2012, such cells can be made nearly 70% transparent to visible light. The cells allegedly can be made in high volume at low cost using solution processing. The cells employ silver nanowire/titanium dioxide composite films as the top electrode, replacing conventional opaque metal electrodes. With this combination, 4% power-conversion efficiency was achieved.
Polymer solar cells have yet to commercially compete with silicon solar cells and other thin-film cells. The present efficiency of polymer solar cells lies near 10%, well below silicon cells. Polymer solar cells also suffer from environmental degradation, lacking effective protective coatings.
Further improvements in performance are needed to promote charge carrier diffusion; transport must be enhanced through control of order and morphology; and interface engineering must be applied to the problem of charge transfer across interfaces.
Polymer solar cells are not widely produced commercially. Starting in 2008, Konarka Technologies started production of polymer-fullerene solar cells. The initial modules were 3–5% efficient, and only last for a few years.
Other third-generation solar cells
- Joachim Luther, Michael Nast, M. Norbert Fisch, Dirk Christoffers, Fritz Pfisterer, Dieter Meissner, Joachim Nitsch "Solar Technology" 2002, Wiley-VCH, 2008 Weinheim. doi:10.1002/14356007.a24_369
- Jørgensen, M., K. Norrman, and F.C. Krebs (2008). "Stability/degradation of polymer solar cells". Solar Energy Materials and Solar Cells 92 (7): 686. doi:10.1016/j.solmat.2008.01.005.
- Po, Riccardo; Carbonera, Chiara; Bernardi, Andrea; Tinti, Francesca; Camaioni, Nadia (2012). "Polymer- and carbon-based electrodes for polymer solar cells: Toward low-cost, continuous fabrication over large area". Solar Energy Materials and Solar Cells 100: 97. doi:10.1016/j.solmat.2011.12.022.
- Scharber, M. C.; Mühlbacher, D.; Koppe, M.; Denk, P.; Waldauf, C.; Heeger, A. J.; Brabec, C. J. (2006). "Design Rules for Donors in Bulk-Heterojunction Solar Cells—Towards 10 % Energy-Conversion Efficiency". Advanced Materials 18 (6): 789. doi:10.1002/adma.200501717.
- Dou, Letian; You, Jingbi; Yang, Jun; Chen, Chun-Chao; He, Youjun; Murase, Seiichiro; Moriarty, Tom; Emery, Keith; Li, Gang; Yang, Yang (2012). "Tandem polymer solar cells featuring a spectrally matched low-bandgap polymer". Nature Photonics 6 (3): 180. Bibcode:2012NaPho...6..180D. doi:10.1038/nphoton.2011.356.
- Kromkout, W.W. (2012-02-13) UCLA engineers create tandem polymer solar cells that set record for energy-conversion. UCLA Newsroom.
- Pivrikas, A.; Sariciftci, N. S.; Juška, G.; Österbacka, R. (2007). "A review of charge transport and recombination in polymer/fullerene organic solar cells". Progress in Photovoltaics: Research and Applications 15 (8): 677. doi:10.1002/pip.791.
- Tessler, Nir; Preezant, Yevgeni; Rappaport, Noam; Roichman, Yohai (2009). "Charge Transport in Disordered Organic Materials and Its Relevance to Thin-Film Devices: A Tutorial Review". Advanced Materials 21 (27): 2741. doi:10.1002/adma.200803541.
- Clarke, Tracey M.; Ballantyne, Amy M.; Nelson, Jenny; Bradley, Donal D. C.; Durrant, James R. (2008). "Free Energy Control of Charge Photogeneration in Polythiophene/Fullerene Solar Cells: The Influence of Thermal Annealing on P3HT/PCBM Blends". Advanced Functional Materials 18 (24): 4029. doi:10.1002/adfm.200800727.
- Xu, Zheng; Chen, Li-Min; Yang, Guanwen; Huang, Chun-Hao; Hou, Jianhui; Wu, Yue; Li, Gang; Hsu, Chain-Shu; Yang, Yang (2009). "Vertical Phase Separation in Poly(3-hexylthiophene): Fullerene Derivative Blends and its Advantage for Inverted Structure Solar Cells". Advanced Functional Materials 19 (8): 1227. doi:10.1002/adfm.200801286.
- Van Bavel, Svetlana; Sourty, Erwan; De With, Gijsbertus; Frolic, Kai; Loos, Joachim (2009). "Relation between Photoactive Layer Thickness, 3D Morphology, and Device Performance in P3HT/PCBM Bulk-Heterojunction Solar Cells". Macromolecules 42 (19): 7396. doi:10.1021/ma900817t.
- Troshin, Pavel A.; Hoppe, Harald; Renz, Joachim; Egginger, Martin; Mayorova, Julia Yu.; Goryachev, Andrey E.; Peregudov, Alexander S.; Lyubovskaya, Rimma N.; Gobsch, Gerhard; Sariciftci, N. Serdar; Razumov, Vladimir F. (2009). "Material Solubility-Photovoltaic Performance Relationship in the Design of Novel Fullerene Derivatives for Bulk Heterojunction Solar Cells". Advanced Functional Materials 19 (5): 779. doi:10.1002/adfm.200801189.
- Moulé, A.J. and K. Meerholz (2008). "Controlling Morphology in Polymer–Fullerene Mixtures". Advanced Materials 20 (2): 240. doi:10.1002/adma.200701519.
- Dang, Minh Trung; Wantz, Guillaume; Bejbouji, Habiba; Urien, Mathieu; Dautel, Olivier J.; Vignau, Laurence; Hirsch, Lionel (2011). "Polymeric solar cells based on P3HT:PCBM: Role of the casting solvent". Solar Energy Materials and Solar Cells 95 (12): 3408. doi:10.1016/j.solmat.2011.07.039.
- Nagarjuna, Gavvalapalli; Venkataraman, Dhandapani (2012). "Strategies for controlling the active layer morphologies in OPVs". Journal of Polymer Science Part B: Polymer Physics 50 (15): n/a. Bibcode:2012JPoSB..50.1045N. doi:10.1002/polb.23073.
- Matthias A. Ruderer and Peter Müller-Buschbaum (2011). "Morphology of polymer-based bulk heterojunction films for organic photovoltaics". Soft Matter 7 (12): 5482. Bibcode:2011SMat....7.5482R. doi:10.1039/C0SM01502D.
- Treat, Neil D.; Brady, Michael A.; Smith, Gordon; Toney, Michael F.; Kramer, Edward J.; Hawker, Craig J.; Chabinyc, Michael L. (2011). "Interdiffusion of PCBM and P3HT Reveals Miscibility in a Photovoltaically Active Blend". Advanced Energy Materials 1: 82. doi:10.1002/aenm.201000023.; Treat, Neil D.; Brady, Michael A.; Smith, Gordon; Toney, Michael F.; Kramer, Edward J.; Hawker, Craig J.; Chabinyc, Michael L. (2011). "Correction: Interdiffusion of PCBM and P3HT Reveals Miscibility in a Photovoltaically Active Blend (Adv. Energy Mater. 2/2011)". Advanced Energy Materials 1 (2): 145. doi:10.1002/aenm.201190008.
- Kozub, Derek R.; Vakhshouri, Kiarash; Orme, Lisa M.; Wang, Cheng; Hexemer, Alexander; Gomez, Enrique D. (2011). "Polymer Crystallization of Partially Miscible Polythiophene/Fullerene Mixtures Controls Morphology". Macromolecules 44 (14): 5722. doi:10.1021/ma200855r.
- Jo, Jang; Kim, Seok-Soon; Na, Seok-In; Yu, Byung-Kwan; Kim, Dong-Yu (2009). "Time-Dependent Morphology Evolution by Annealing Processes on Polymer:Fullerene Blend Solar Cells". Advanced Functional Materials 19 (6): 866. doi:10.1002/adfm.200800968.
- Collins, Brian A.; Gann, Eliot; Guignard, Lewis; He, Xiaoxi; McNeill, Christopher R.; Ade, Harald (2010). "Molecular Miscibility of Polymer−Fullerene Blends". The Journal of Physical Chemistry Letters 1 (21): 3160. doi:10.1021/jz101276h. Supporting information
- Tremolet De Villers, Bertrand; Tassone, Christopher J.; Tolbert, Sarah H.; Schwartz, Benjamin J. (2009). "Improving the Reproducibility of P3HT:PCBM Solar Cells by Controlling the PCBM/Cathode Interface". The Journal of Physical Chemistry C 113 (44): 18978. doi:10.1021/jp9082163.
- Yin, W. and M. Dadmun, "A New Model for the Morphology of P3HT/PCBM Organic Photovoltaics from Small-Angle Neutron Scattering: Rivers and Streams" ACS Nano, 2011, volume 5, p. 4756-4768.
- Nilsson, Svante; Bernasik, Andrzej; Budkowski, Andrzej; Moons, Ellen (2007). "Morphology and Phase Segregation of Spin-Casted Films of Polyfluorene/PCBM Blends". Macromolecules 40 (23): 8291. Bibcode:2007MaMol..40.8291N. doi:10.1021/ma070712a.
- Lecover, Rachel; Williams, Nicholas; Markovic, Nina; Reich, Daniel H.; Naiman, Daniel Q.; Katz, Howard E. (2012). "Next-Generation Polymer Solar Cell Materials: Designed Control of Interfacial Variables". ACS Nano 6 (4): 2865–70. doi:10.1021/nn301140w. PMID 22444948.
- Pivrikas, Almantas; Neugebauer, Helmut; Sariciftci, Niyazi Serdar (2011). "Influence of processing additives to nano-morphology and efficiency of bulk-heterojunction solar cells: A comparative review". Solar Energy 85 (6): 1226. Bibcode:2011SoEn...85.1226P. doi:10.1016/j.solener.2010.10.012.
- Yao, Yan; Hou, Jianhui; Xu, Zheng; Li, Gang; Yang, Yang (2008). "Effects of Solvent Mixtures on the Nanoscale Phase Separation in Polymer Solar Cells". Advanced Functional Materials 18 (12): 1783. doi:10.1002/adfm.200701459.
- Lee, Jae Kwan; Ma, Wan Li; Brabec, Christoph J.; Yuen, Jonathan; Moon, Ji Sun; Kim, Jin Young; Lee, Kwanghee; Bazan, Guillermo C.; Heeger, Alan J. (2008). "Processing Additives for Improved Efficiency from Bulk Heterojunction Solar Cells". Journal of the American Chemical Society 130 (11): 3619–23. doi:10.1021/ja710079w. PMID 18288842.
- Rogers, James T.; Schmidt, Kristin; Toney, Michael F.; Bazan, Guillermo C.; Kramer, Edward J. (2012). "Time-Resolved Structural Evolution of Additive-Processed Bulk Heterojunction Solar Cells". Journal of the American Chemical Society 134 (6): 2884–7. doi:10.1021/ja2104747. PMID 22276735.
- Liang, Yongye; Xu, Zheng; Xia, Jiangbin; Tsai, Szu-Ting; Wu, Yue; Li, Gang; Ray, Claire; Yu, Luping (2010). "For the Bright Future—Bulk Heterojunction Polymer Solar Cells with Power Conversion Efficiency of 7.4%". Advanced Materials 22 (20): E135–8. doi:10.1002/adma.200903528. PMID 20641094.
- Li, Weiwei; Zhou, Yi; Viktor Andersson, B.; Mattias Andersson, L.; Thomann, Yi; Veit, Clemens; Tvingstedt, Kristofer; Qin, Ruiping; Bo, Zhishan; Inganäs, Olle; Würfel, Uli; Zhang, Fengling (2011). "The Effect of additive on performance and shelf-stability of HSX-1/PCBM photovoltaic devices". Organic Electronics 12 (9): 1544. doi:10.1016/j.orgel.2011.05.028.
- Beaujuge, P.M. and J.M.J. Fréchet (2011). "Molecular Design and Ordering Effects in π-Functional Materials for Transistor and Solar Cell Applications". Journal of the American Chemical Society 133 (50): 20009–29. doi:10.1021/ja2073643. PMID 21999757.
- Troshin, Pavel A.; Koeppe, Robert; Peregudov, Alexander S.; Peregudova, Svetlana M.; Egginger, Martin; Lyubovskaya, Rimma N.; Sariciftci, N. Serdar (2007). "Supramolecular Association of Pyrrolidinofullerenes Bearing Chelating Pyridyl Groups and Zinc Phthalocyanine for Organic Solar Cells". Chemistry of Materials 19 (22): 5363. doi:10.1021/cm071243u.
- Tevis, Ian D.; Tsai, Wei-Wen; Palmer, Liam C.; Aytun, Taner; Stupp, Samuel I. (2012). "Grooved Nanowires from Self-Assembling Hairpin Molecules for Solar Cells". ACS Nano 6 (3): 2032–40. doi:10.1021/nn203328n. PMID 22397738.
- Dössel, L.F.; Kamm, Valentin; Howard, Ian A.; Laquai, Frédéric; Pisula, Wojciech; Feng, Xinliang; Li, Chen; Takase, Masayoshi et al. (2012). "Synthesis and Controlled Self-Assembly of Covalently Linked Hexa-peri-hexabenzocoronene/Perylene Diimide Dyads as Models To Study Fundamental Energy and Electron Transfer Processes". Journal of the American Chemical Society 134 (13): 5876–86. doi:10.1021/ja211504a. PMID 22394147.
- Miyanishi, Shoji; Zhang, Yue; Tajima, Keisuke; Hashimoto, Kazuhito (2010). "Fullerene attached all-semiconducting diblock copolymers for stable single-component polymer solar cells". Chemical Communications 46 (36): 6723–5. doi:10.1039/C0CC01819H. PMID 20717605.
- Sary, Nicolas; Richard, Fanny; Brochon, Cyril; Leclerc, Nicolas; Lévêque, Patrick; Audinot, Jean-Nicolas; Berson, Solenn; Heiser, Thomas et al. (2010). "A New Supramolecular Route for Using Rod-Coil Block Copolymers in Photovoltaic Applications". Advanced Materials 22 (6): 763–8. doi:10.1002/adma.200902645. PMID 20217786.
- Lin, Ying; Lim, Jung Ah; Wei, Qingshuo; Mannsfeld, Stefan C. B.; Briseno, Alejandro L.; Watkins, James J. (2012). "Cooperative Assembly of Hydrogen-Bonded Diblock Copolythiophene/Fullerene Blends for Photovoltaic Devices with Well-Defined Morphologies and Enhanced Stability". Chemistry of Materials 24 (3): 622. doi:10.1021/cm203706h.
- Topham, Paul D.; Parnell, Andrew J.; Hiorns, Roger C. (2011). "Block copolymer strategies for solar cell technology". Journal of Polymer Science Part B: Polymer Physics 49 (16): 1131. doi:10.1002/polb.22302.
- Barrau, Sophie; Heiser, Thomas; Richard, Fanny; Brochon, Cyril; Ngov, Chheng; Van De Wetering, Karin; Hadziioannou, Georges; Anokhin, Denis V.; Ivanov, Dimitri A. (2008). "Self-Assembling of Novel Fullerene-Grafted Donor–Acceptor Rod−Coil Block Copolymers". Macromolecules 41 (7): 2701. Bibcode:2008MaMol..41.2701B. doi:10.1021/ma7022099.
- "Scientists create highly transparent solar cells for windows that generate electricity". Phys.org. Retrieved 2012-07-23.
- For a similar graph, see: Hoppe, Harald; Sariciftci, N. Serdar (2008). "Polymer Solar Cells". Photoresponsive Polymers II. pp. 1–86 (4). doi:10.1007/12_2007_121. ISBN 978-3-540-69452-6.
- Kevin Bullis. Mass Production of Plastic Solar Cells, Technology Review Magazine, October 17, 2008.
- N.S. Sariciftci, L. Smilowitz, A.J. Heeger,F. Wudl, Photoinduced Electron Transfer from Conducting Polymers onto Buckminsterfullerene, Science 258, (1992) 1474
- N.S. Sariciftci, A.J. Heeger, Photophysics, charge separation and device applications of conjugated polymer/fullerene composites, in Handbook of Organic Conductive Molecules and Polymers, edited by H.S.Nalwa, 1, Wiley, Chichester, New York, 1997, Ch. 8, p.p. 413–455
- „Plastic Solar Cells“ Christoph J. Brabec, N. Serdar Sariciftci, Jan Kees Hummelen, Advanced Functional Materials, Vol. 11 No: 1, pp. 15–26 (2001)
- Organic Photovoltaics”, Christoph Brabec, Vladimir Dyakonov, Jürgen Parisi and Niyazi Serdar Sariciftci (eds.), Springer Verlag (2003) ISBN 3-540-00405X
- Organic Photovoltaics: Mechanisms, Materials, and Devices (Optical Engineering), (Sam-Shajing Sun and Niyazi Serdar Sariciftci (eds.), CRC Press (Taylor&Francis Group) ISBN 0-8247-5963-X, Boca Raton, 2005
- A. Mayer, S. Scully, B. Hardin, M. Rowell, M. McGehee, Polymer-based solar cells, Materials Today 10, (2007) 28. doi:10.1016/S1369-7021(07)70276-6
- H. Hoppe and N. S. Sariciftci, Polymer Solar Cells, p. 1–86, in Photoresponsive Polymers II, Eds.: S. R. Marder and K.-S. Lee, Advances in Polymer Science, Springer, ISBN 978-3-540-69452-6, Berlin-Heidelberg (2008)
- NREL reports
- LIOS – Linzer Institut für Organische Solarzellen, Johannes Kepler Universität Linz, Österreich
- Quantsol 1998
- Organic Solar Cells - Theory and Practice (Coursera)