In-Situ Generation of Non-Toxic Acceptor Materials for Use in Hybrid Photovoltaics
Saif Haque a, Andrew MacLachlan a, Jenny Nelson b
a Department of Chemistry, Imperial College London, South Kensington Campus London, London, United Kingdom
b Department of Physics, Imperial College London, United Kingdom
International Conference on Hybrid and Organic Photovoltaics
Proceedings of 6th International Conference on Hybrid and Organic Photovoltaics (HOPV14)
Ecublens, Switzerland, 2014 May 11th - 14th
Organizers: Michael Graetzel and Mohammad Nazeeruddin
Poster, Andrew MacLachlan, 103
Publication date: 1st March 2014

The use of inorganic nanoparticles as acceptor materials in photovoltaic devices has seen promising increases in efficiency over recent years, with current records using P3HT as a donor polymer rivaling the traditional all organic systems.  Using nanoparticles as a replacement for organic acceptors has a variety of advantages including increased mobility, chemical stability, cost of synthesis and the ability of the acceptor also to absorb light.  The ability to absorb light is key in increasing currents generated by high efficiency devices by covering more of the solar spectrum but also we have recently shown the hole transfer process from the inorganic component to polymer to be more efficient than the converse electron transfer process.1

One of the major challenges with these so called hybrid solar cells is the difficulty in processing both the inorganic and organic components from a common solvent.  This problem is traditionally overcome by the use of solublising capping ligands bound to the surface of the nanoparticles.  These ligands allow the materials to be solution processed together, but they also directly inhibit charge generation.  We reported an in-situ method for the production of the inorganic component within the polymer after co-deposition by utilizing the decomposition of metal xanthate complexes.2 This allows for a one pot ligand free generation of these heterojunctions and has been shown to give superior charge generation and higher efficiency in photovoltaic devices when compared to an equivalent ex-situ capped nanoparticle system.3

As well as a ligand free heterojunction the use of xanthate precursors also opens up the possibility of synthesising a variety of sulfide materials that have not previously been fully explored, including several relatively non-toxic materials in comparison to the current materials of choice, namely cadmium sulfide.  We present the synthesis of non-toxic heterojunctions of bismuth sulfide and antimony sulfide for use in hybrid photovoltaics.  The control of these heterojunction is studied by tuning of the xanthate precusors and through a variety of processing techniques.  These materials are characterised using a variety of techniques including SEM, TEM and XRD and spectroscopic studies of charge photogeneration using transient absorption spectroscopy (TAS) are used along with the fabrication of photovoltaic devices.


Schematic diagram illustrating the fabrication method of in-situ hybrid organic-inorganic heterojunctions.
Dowland, S. A.; Reynolds, L. X.; MacLachlan, A.; Cappel, U. B.; Haque, S. A. Journal of Materials Chemistry A 2013, 1, 13896. Leventis, H. C.; King, S. P.; Sudlow, A.; Hill, M. S.; Molloy, K. C.; Haque, S. A. Nano Letters 2010, 10, 1253. Reynolds, L. X.; Lutz, T.; Dowland, S.; MacLachlan, A.; King, S.; Haque, S. A. Nanoscale 2012, 4, 1561.
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