  Usually, single-crystal material has a longer carrier diffusion length due to
fewer defects. Here, we report a nano/amorphous copper oxide and selenium (COS)
composite film prepared by radio frequency magnetron co-sputtering of CuO and
Se and post annealing. The photo-generated carriers in the COS film can diffuse
very far (3.147 mm). Additionally, the COS film can strongly absorb light over
the entire solar spectrum region (250-2500 nm) (average absorptance is ~80%).
These results indicate that the COS composite is an excellent material and can
be used in solar cells and other photo-electric devices.
