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Modifications in Morphology Resulting from Nanoimprinting Bulk Heterojunction Blends for Light Trapping Organic Solar Cell Designs
journal contribution
posted on 2013-08-28, 00:00 authored by John R. Tumbleston, Abay Gadisa, Yingchi Liu, Brian A. Collins, Edward T. Samulski, Rene Lopez, Harald AdeNanoimprinting
the photoactive layer of bulk heterojunction (BHJ) organic solar cells
is a promising technique for enhancing device performance via improved
light absorption. Here, we demonstrate that imprinting poly(3-hexylthiophene)
(P3HT) and fullerene BHJ blends leads to adverse morphological changes
within the photoactive nanopattern which have been previously overlooked.
In particular, nanoimprinting induces a factor of 2 difference in
polymer:fullerene composition between the nanopattern posts and interconnecting
flash layer that inadvertently moves the composition outside the range
for optimal performance. This occurs because of the strong tendency
of regioregular P3HT to crystallize since imprinting blends based
on amorphous regiorandom P3HT have uniform nanopattern composition.
Based on these results, we outline promising design strategies, such
as nanoimprinting amorphous polymers, to serve as guidelines for fabricating
high-performance nanopatterned BHJ solar cells capable of maximized
light absorption.