Molecular orientation and performance of nanoimprinted polymer-based blend thin film solar cells

In this work, we have used synchrotron-based grazing incidence X-ray scattering to measure the molecular orientation and morphology of nanostructured thin films of blended poly(3-hexylthiophene)/[6,6]-phenyl C61-butyric acid methyl ester blends patterned with nanoimprint lithography. Imprinting the blend films at 150 °C results in significant polymer chain orientational anisotropy, in contrast to patterning the film at only 100 °C. The temperature-dependent evolution of the X-ray scattering data reveals that the imprint-induced polymer reorientation remains at high temperatures even after the patterned topographic features vanish upon melting. Photovoltaic devices fabricated from the blend films imprinted at 150 °C exhibit a ∼21% improvement in power conversion efficiency compared to those imprinted at 100 °C, consistent with a polymer chain configuration better suited to charge carrier collection.