ZnO nanocolumns arrays for thin film silicon solar cells

Hydrothermal growth offers possibility to deposit directly high optical and electronic quality ZnO in a form of nanorods or nanocolumns at low temperature over large areas. This can be advantageous for a recently presented 3-dimensional design of thin film silicon solar cells [1].

I report on hydrothermal growth of single (or multi)-crystalline ZnO nanocolumns arrays, perpendicularly oriented towards TCO (transparent conductive oxide) substrate. In order to get well defined spacing and arrangement over the area, we used electron beam lithography and laser interference lithography. Vertically aligned ZnO nanocolumns were grown in an aqueous solution of zinc nitrate hexahydrate and hexamethylenetetramine at 75÷95 ºC, with the growth rate 0.5÷1μm/h.

The morphology of the nanostructures was visualized by scanning electron microscopy. Electrical, optical and surface properties of ZnO nanocolumns, which are decisive for the high solar cell efficiency, were investigated in details by optical and photothermal spectroscopy.

In this presentation, I will show our results on optimization of nanostructured TCO/glass substrates being designed for very thin amorphous Si cells and for tandem a-Si/a-Si and a-Si/microcrystalline Si solar cells with a high efficiency potential.

[1] M. Vanecek, O. Babchenko, A. Purkrt, J. Holovsky, N. Neykova, A. Poruba, Z. Remes, J. Meier, U. Kroll: Appl. Phys. Lett. 98, 163503 (2011)