Abstract
The topic of this chapter will be a detailed investigation of current-voltage data of the model system ZnPc:C\(_{60}\). We start by explaining the influence of the donor:acceptor mixing ratio on the open-circuit voltage. Then, we investigate a possible optimization of the morphology in the bulk heterojunction by using a vertical concentration gradient of donor and acceptor. The main focus of the further parts of this chapter is on the role of recombination and charge transport governing the power-conversion efficiency. By manipulating spatial absorption profiles in the bulk heterojunction we conclude that charge extraction and recombination between charges are the competing processes limiting the fill factor. An investigation of the open-circuit voltage as a function of illumination intensity allows us to discriminate between direct, indirect, and surface recombination. In particular, this chapter addresses the following questions: (a) What are possible explanations for different open-circuit voltages of devices consisting of the same active material system (e.g. when changing the mixing ratio)? (b) What are simple experiments to identify the correct reason? (c) Which explanations exist for a changed donor-acceptor gap in a bulk heterojunction based on the same materials? (d) Why is it interesting to investigate graded junctions? (e) What are possible explanations for the fill factor depending on the color of the illumination? What is the role of charge-carrier mobility? (f) Why does the internal quantum efficiency depend on the wavelength of the incident light and on the thickness of the optical spacer? What is the consequence for the spectral mismatch factor? (g) What point of the J-V curve is a good choice to investigate the dominating recombination mechanisms in a solar cell? How can this be done? (h) What does the diode ideality factor tell?
The results shown in Sect. 8.1 are published in [1] and those of Sect. 8.2 in [2]; parts of Sect. 8.3 in [3] and parts of Sect. 8.4 in [4].
This is a preview of subscription content, log in via an institution to check access.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
References
Tress, W., Pfuetzner, S., Leo, K., Riede, M.: Open circuit voltage and IV curve shape of ZnPc:C60 solar cells with varied mixing ratio and hole transport layer. J. Photonics Energy 1, 011114 (2011)
Tress, W., Leo, K., Riede, M.: Effect of concentration gradients in ZnPc:C60 bulk heterojunction organic solar cells. Sol. Energy Mater. Sol. Cells 95, 2981–2986 (2011)
Tress, W., Merten, A., Furno, M., Hein, M., Leo, K., Riede, M.: Correlation of absorption profile and fill factor in organic solar cells: the role of mobility imbalance. Adv. Energy Mater. 3, 631–638 (2013)
Tress, W., Leo, K., Riede, M.: Dominating recombination mechanisms in organic solar cells based on ZnPc and C60. Appl. Phys. Lett. 102, 163901 (2013)
Heutz, S., Sullivan, P., Sanderson, B.M., Schultes, S.M., Jones, T.S.: Influence of molecular architecture and intermixing on the photovoltaic, morphological and spectroscopic properties of CuPc-C60 heterojunctions. Sol. Energy Mater. Sol. Cells 83, 229–245 (2004)
Kim, Y., Choulis, S.A., Nelson, J., Bradley, D.D.C., Cook, S., Durrant, J.R.: Composition and annealing effects in polythiophene/fullerene solar cells. J. Mater. Sci. 40, 1371–1376 (2005)
Sakai, J., Taima, T., Saito, K.: Efficient oligothiophene:fullerene bulk heterojunction organic photovoltaic cells. Org. Electron. 9, 582–590 (2008)
Piersimoni, F., Chambon, S., Vandewal, K., Mens, R., Boonen, T., Gadisa, A., Izquierdo, M., Filippone, S., Ruttens, B., D’Haen, J., Martin, N., Lutsen, L., Vanderzande, D., Adriaensens, P., Manca, J.V.: Influence of fullerene ordering on the energy of the charge-transfer state and open-circuit voltage in polymer:fullerene solar cells. J. Phys. Chem. C 115, 10873–10880 (2011)
Tietze, M.L., Tress, W., Pfützner, S., Schünemann, C., Burtone, L., Riede, M., Leo, K.,Vandewal, K., Olthof, S., Schulz, P., Kahn, A.: Correlation of open-circuit voltage and energy levels in zinc-phthalocyanine: C\(_{60}\) bulk heterojunction solar cells with varied mixing ratio. Phys. Rev. B 88, 085119 (2013)
Vandewal, K., Goris, L., Haeldermans, I., Nesladek, M., Haenen, K., Wagner, P., Manca, J.V.: Fourier-transform photocurrent spectroscopy for a fast and highly sensitive spectral characterization of organic and hybrid solar cells. Thin Solid Films 516, 7135–7138 (2008)
Jamieson, F.C., Domingo, E.B., McCarthy-Ward, T., Heeney, M., Stingelin, N., Durrant, J.R.: Fullerene crystallisation as a key driver of charge separation in polymer/fullerene bulk heterojunction solar cells. Chem. Sci. 3, 485 (2012)
Sullivan, P., Heutz, S., Schultes, S.M., Jones, T.S.: Influence of codeposition on the performance of CuPc-C60 heterojunction photovoltaic devices. Appl. Phys. Lett. 84, 1210–1212 (2004)
Drees, M., Davis, R.M., Heflin, J.R.: Improved morphology of polymer-fullerene photovoltaic devices with thermally induced concentration gradients. J. Appl. Phys. 97, 036103 (2005)
Kaur, M., Gopal, A., Davis, R.M., Heflin, J.R.: Concentration gradient P3OT/PCBM photovoltaic devices fabricated by thermal interdiffusion of separately spin-cast organic layers. Sol. Energy Mater. Sol. Cells 93, 1779–1784 (2009)
Chen, L., Tang, Y., Fan, X., Zhang, C., Chu, Z., Wang, D., Zou, D.: Improvement of the efficiency of CuPc/C60-based photovoltaic cells using a multistepped structure. Org. Electron. 10, 724–728 (2009)
Schünemann, C., Wynands, D., Wilde, L., Hein, M.P., Pfützner, S., Elschner, C., Eichhorn, K.-J., Leo, K., Riede, M.: Phase separation analysis of bulk heterojunctions in small-molecule organic solar cells using zinc-phthalocyanine and C\(_{60}\). Phys. Rev. B 85, 245314 (2012)
Tress, W., Leo, K., Riede, M.: Photoconductivity as loss mechanism in organic solar cells. Phys. Status Solidi RRL 7, 401–405 (2013)
Tanase, C., Meijer, E.J., Blom, P.W.M., Leeuw, D.M.: Unification of the hole transport in polymeric field-effect transistors and light-emitting diodes. Phys. Rev. Lett. 91, 216601 (2003)
Harada, K., Werner, A., Pfeiffer, M., Bloom, C., Elliott, C., Leo, K.: Organic homojunction diodes with a high built-in potential: interpretation of the current-voltage characteristics by a generalized Einstein relation. Phys. Rev. Lett. 94, 036601 (2005)
Wetzelaer, G.A.H., Kuik, M., Lenes, M., Blom, P.W.M.: Origin of the dark-current ideality factor in polymer:fullerene bulk heterojunction solar cells. Appl. Phys. Lett. 99, 153506 (2011)
Wetzelaer, G.A.H., Koster, L.J.A., Blom, P.W.M.: Validity of the Einstein relation in disordered organic semiconductors. Phys. Rev. Lett. 107, 066605 (2011)
Shuttle, C.G., Maurano, A., Hamilton, R., O’Regan, B., Mello, J.C., Durrant, J.R.: Charge extraction analysis of charge carrier densities in a polythiophene/fullerene solar cell: analysis of the origin of the device dark current. Appl. Phys. Lett. 93, 183501 (2008)
Maurano, A., Hamilton, R., Shuttle, C.G., Ballantyne, A.M., Nelson, J., O’Regan, B., Zhang, W., McCulloch, I., Azimi, H., Morana, M., Brabec, C.J., Durrant, J.R.: Recombination dynamics as a key determinant of open circuit voltage in organic bulk heterojunction solar cells: a comparison of four different donor polymers. Adv. Mater. 22, 4987–4992 (2010)
Li, Z., Gao, F., Greenham, N.C., McNeill, C.R.: Comparison of the operation of polymer/fullerene, polymer/polymer, and polymer/nanocrystal solar cells: a transient photocurrent and photovoltage study. Adv. Funct. Mater. 21, 1419–1431 (2011)
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
Copyright information
© 2014 Springer International Publishing Switzerland
About this chapter
Cite this chapter
Tress, W. (2014). The Model System ZnPc:C\(_{60}\) . In: Organic Solar Cells. Springer Series in Materials Science, vol 208. Springer, Cham. https://doi.org/10.1007/978-3-319-10097-5_8
Download citation
DOI: https://doi.org/10.1007/978-3-319-10097-5_8
Published:
Publisher Name: Springer, Cham
Print ISBN: 978-3-319-10096-8
Online ISBN: 978-3-319-10097-5
eBook Packages: Chemistry and Materials ScienceChemistry and Material Science (R0)