ORGANICPV
polymer:fullerene devices as well as improve the throughput of the technique.
Coupling broad spectrum illumination with the pcAFM and trEFM setups would also allow for spectral analysis of optoelectronic behavior. Further pcAFM work is currently underway in several groups using lower work function tips so as to avoid some of the limitations discussed above and perhaps achieve better quantitative agreement between EQE and spatially-averaged photocurrent on different donor/acceptor blend ratio devices.
While the techniques here are presented in the context of OPV morphology, it should be stressed that they can also be useful in other photoactive technologies.
For example, solid-state dye sensitized solar cells30 or composite photocatalysts31
are expected to
exhibit local heterogeneity that would ultimately impact electrical performance. trEFM and pcAFM therefore have the potentialprovide ideal tools for characterizing these differing types of photovoltaic solar systems.
References
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14.Hoppe, H. et al. Kelvin probe force microscopy study on conjugated polymer/fullerene bulk heterojunction organic solar cells. Nano Lett. 5, 269 (2005). 15.Maturová, K., Kemerink, M., Wienk, M. M. and Charrier, D. S. H. Scanning kelvin probe microscopy on bulk heterojunction polymer blends. Adv. Func. Mater. (2009). 16.Palermo, V., Palma, M. and Samori, P. Electronic characterization of organic thin films by Kelvin probe force microscopy. Adv. Mat. 18, 145—164 (2006). 17.McNeill, C. R., Frohne, H., Holdsworth, J. L. and Dastoor, P. C. Near-field scanning photocurrent measurements of
polyfluorene blend devices: directly correlating morphology with current generation. Nano Lett. 4, 2503 (2004). 18.Riehn, R. et al. Local probing of photocurrent and photoluminescence in a phase-separated conjugated-polymer blend by means of near-field excitation. Adv. Func. Mater. 16, 469 (2006).
19.Romero, M. J., Morfa, A. J., Reilly III, T. H., van de Lagemaat, J. and Al-Jassim, M. Nanoscale imaging of exciton transport in organic photovoltaic semiconductors by tip-enhanced tunneling luminescence. Nano Lett. 9, 3904 (2009). 20.Pingree, L. S. C., Reid, O. G. and Ginger, D. S. Electrical scanning probe microscopy on active organic electronic devices. Adv. Mater. 21, 19 (2009). 21.Groves, C., Reid, O. G. and Ginger, D. S. Heterogeneity in polymer solar cells: local morphology and performance in organic photovoltaics studied with scanning probe microscopy. Acc. Chem. Res., in press. 22.Coffey, D. C., Reid, O. G., Rodovsky, D. B., Bartholomew, G. P. and Ginger, D. S. Mapping local photocurrents in polymer/fullerene solar cells with photoconductive atomic force microscopy. Nano Lett. 7, 738 (2007). 23.Pingree, L. S. C., Reid, O. G. and Ginger, D. S. Imaging the evolution of nanoscale photocurrent collection and transport networks during annealing of polythiophene/fullerene solar cells. Nano Lett. 9, 2946 (2009). 24.Coffey, D. C. and Ginger, D. S. Time-resolved electrostatic force microscopy of polymer solar cells. Nat. Mater. 5, 735 (2006).
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