Luria, J.L. and Hoepker, N. and Bruce, R. and Jacobs, A.R. and Groves, C. and Marohn, J.A. (2012) 'Spectroscopic imaging of photopotentials and photoinduced potential fluctuations in a bulk heterojunction solar cell film.', ACS nano., 6 (11). pp. 9392-9401.
We present spatially resolved photovoltage spectra of a bulk heterojunction solar cell film composed of phase-separated poly(9,9′-dioctylfluorene-co-benzothiadiazole) (F8BT) and poly(9,9′-dioctylfluorene-co-bis-N,N′-(4-butylphenyl)-bis-N,N′-phenyl-1,4-phenylenediamine) (PFB) polymers prepared on ITO/PEDOT:PSS and aluminum substrates. Over both PFB- and F8BT-rich domains, the photopotential spectra were found to be proportional to a linear combination of the polymers’ absorption spectra. Charge trapping in the film was studied using photopotential fluctuation spectroscopy, in which low-frequency photoinduced electrostatic potential fluctuations were measured by observing noise in the oscillation frequency of a nearby charged atomic force microscope cantilever. Over both F8BT- and PFB-rich regions, the magnitude, distance dependence, frequency dependence, and illumination wavelength dependence of the observed cantilever frequency noise are consistent with photopotential fluctuations arising from stochastic light-driven trapping and detrapping of charges in F8BT. Taken together, our findings suggest a microscopic mechanism by which intermixing of phases leads to charge trapping and thereby to suppressed open-circuit voltage and decreased efficiency in this prototypical bulk heterojunction solar cell film.
|Keywords:||PFB, P8BT solar cell, Open-circuit voltage, Scanning Kelvin probe microscopy, Photovoltage and photopotential fluctuation spectroscopy.|
|Full text:||Full text not available from this repository.|
|Publisher Web site:||http://dx.doi.org/10.1021/nn300941f|
|Date accepted:||No date available|
|Date deposited:||No date available|
|Date of first online publication:||November 2012|
|Date first made open access:||No date available|
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