24 research outputs found
Time-independent, high electron mobility in thin PC 61 BM films: Relevance to organic photovoltaics
Elemental Mapping of Interfacial Layers at the Cathode of Organic Solar Cells
One of the limitations in understanding
the performance of organic
solar cells has been the unclear picture of morphology and interfacial
layers developed at the active layer/cathode interface. Here, by utilizing
the shadow-Focused Ion Beam technique to enable energy-filtered transmission
electron microscopy imaging in conjunction with X-ray photoelectron
spectroscopy (XPS) experiments, we examine the cross-section of polythiophene/fullerene
solar cells to characterize interfacial layers near the semiconductor-cathode
interface. Elemental mapping reveals that localization of fullerene
to the anode interface leads to low fill factors and S-shaped current–voltage
characteristics. Furthermore, the combination of elemental mapping
and XPS depth profiles of devices demonstrate oxidation of the aluminum
cathode at the active layer interface for devices without S-shaped
characteristics and fill factors of 0.6. The presence of a thin dielectric
at the semiconductor-cathode interface could minimize electronic barriers
for charge extraction by preventing interfacial charge reorganization
and band-bending