In-plane anisotropy of photovoltaic effects in aligned polymer solar cells

We herein describe our investigation of in-plane anisotropic polymer photovoltaic effects in aligned bulk-heterojunction layers that consisted of an oriented composite of regioregular poly(3-hexylthiophene) and methanofullerene (P3HT:PCBM). By means of simple rubbing, a fairly uniform in-plane alignment of the P3HT:PCBM layer was achieved. The macroscopic orientation of the main chain of the P3HT polymer in the aligned layer was observed to be significantly greater in the direction of rubbing, while the nanoscopic crystalline packing along the side chains of the P3HT decreased significantly. The polymer solar cells that contained aligned P3HT:PCBM photoactive films exhibited a greater degree of anisotropy of the photovoltaic effects under polarized illumination along the two principal axes. These findings form a promising foundation for new types of polarization-dependent opto-electrical applications.