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We present a methodology for probing light-matter interactions in prototype photovoltaic devices consisting of an organic semiconductor active layer with a semitransparent metal electrical contact exhibiting surface plasmon-based enhanced optical transmission. We achieve high-spectral irradiance in a spot size of less than 100 μm using a high-brightness laser-driven light source and appropriate coupling optics. Spatially resolved Fourier transform photocurrent spectroscopy in the visible and near-infrared spectral regions allows us to measure external quantum efficiency with high sensitivity in small-area devices (<1 mm2). This allows for rapid fabrication of variable-pitch sub-wavelength hole arrays in metal films for use as transparent electrical contacts, and evaluation of the evanescent and propagating mode coupling to resonances in the active layer. [ABSTRACT FROM AUTHOR]

Material properties in polymer and fullerene bulk heterojunctions (BHJs) such as donor to acceptor volume fraction, morphology, and molecular orientation critically influence light absorption, exciton dissociation, charge transport, and recombination, all of which are crucial device properties in organic photovoltaics (OPV). Spatial variation of BHJ properties normal to the substrate, caused by phase segregation, can thereby create corresponding spatial variations in the OPVs optoelectronic properties. Here, normally incident and wave-guided optical modes are used to selectively excite localized regions within an inverted poly(3-hexythiophene-2,5-diyl) and phenyl-C61-butyric acid methyl ester BHJ OPV and corresponding internal quantum efficiencies are measured to study the spatial-dependent charge carrier collection probability within the BHJ. An electron-limited charge collection profile is observed for a thick (920 nm) BHJ due to fullerene-poor regions as a result of phase segregation. As the thickness of the BHJ is reduced (100 nm), charge transport is seen to be unaffected by the phase segregation. This has the potential to be a versatile non-destructive characterization technique for measuring the spatially varying charge collection probability in thin film photovoltaics and will help enable optimum device design and characterization. [ABSTRACT FROM AUTHOR]

In article 1300525, D. M. Nanditha M. Dissanayake and co‐workers show that unlike the behavior observed thicknesses typically used for devices (100 nm), electron‐limited behavior is seen for a thicker active layer (920 nm) due to phase segregation in poly(3‐hexythiophene‐2,5‐diyl):phenyl‐C61‐butyric acid methyl ester (P3HT:PCBM). The illustration shows prism‐coupled guidedmodes used for spatially selective excitation in a P3HT:PCBM photovoltaic, which are used to obtain high‐resolution profiles of charge‐collection probability in the photoactive layer. [ABSTRACT FROM AUTHOR]