Morphological evolution of porous nanostructures grown from a single isolated anodic alumina nanochannel.

Porous anodic aluminum oxide (AAO) membranes have been widely used as templates for growing nanomaterials because of their ordered nanochannel arrays with high aspect ratio and uniform pore diameter. However, the intrinsic growth behavior of an individual AAO nanochannel has never been carefully studied for the lack of a means to fabricate a single isolated anodic alumina nanochannel (SIAAN). In this study, we develop a lithographic method for fabricating a SIAAN, which grows into a porous hemispherical structure with its pores exhibiting fascinating morphological evolution during anodization. We also discover that the mechanical stress affects the growth rate and pore morphology of AAO porous structures. This study helps reveal the growth mechanism of arrayed AAO nanochannels grown on a flat aluminum surface and provides insights to help pave the way to altering the geometry of nanochannels on AAO templates for the fabrication of advanced nanocomposite materials.

Nanostructured nanorod arrays presenting TiO2 nanorods/poly(3-hexylthiophene) for solar cells application.

We have fabricated inverted heterojunction solar cell devices incorporating titanium dioxide nanorod/poly(3-hexylthiophene) (P3HT) rod arrays using melt-assisted anodic alumina oxide template. Using transmission electron microscopy and conductance atomic force microscopy, we revealed that phase-separated TiO2 rich (n-type) and P3HT rich (p-type) regions presents in these rod arrays. The optimized composite rod array structure had a higher hole mobility than that of the blend film consisting of TiO2 nanorod and P3HT as determined by fitting the dark J-V curves into the space charge-limited current model. The more efficient carrier transport of the device incorporating the nanorod arrays provided it with both a higher short-circuit current density and power conversion efficiency.

Inverted heterojunction solar cells incorporating fullerene/polythiophene composite core/shell nanorod arrays.

We have fabricated inverted heterojunction solar cell devices incorporating [6,6]-phenyl-C(61)-butyric acid methyl ester/poly(3-hexylthiophene) core/shell nanorod arrays by using an anodic alumina oxide template. The internal quantum efficiencies and external quantum efficiencies of these core/shell nanorod inverted solar cells were higher than those of the corresponding conventional inverted bulk heterojunction device. The optimized nanorod array structure had a high hole mobility that was over one order magnitude greater than that of the conventional bulk heterojunction structure, as determined by fitting the dark J-V curves into the space charge limited current model. The more efficient carrier transport of the device incorporating the core/shell nanorod arrays provided it with both a higher short-circuit current density and power conversion efficiency.

Ordered polythiophene/fullerene composite core-shell nanorod arrays for solar cell applications.

For the first time, we have used melt-assisted wetting of porous alumina templates to prepare ordered core-shell nanorod arrays of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM) for use in polymer solar cells. We characterized these arrays using tunneling electron microscopy and conductance atomic force microscopy, which revealed the presence of phase-separated shell (p-type) and core (n-type) regions. Under illumination, we observed a variation of several picoamperes between the currents in the core and shell regions of the P3HT/PCBM nanorod arrays.