In mid-2006, Kyosemi Corp. plans to begin full-scale mass production of its Sphelar spherical micro solar cell at its Eniwa Operation in Eniwa City, Hokkaido, Japan. While existing planar solar cells [...]]]> Kyosemi Corporation is developing solar cells consisting of 1mm spheres on a flexible substrate.
More information on the Sphelar solar cells: production process, main features, overview (PDF):

In mid-2006, Kyosemi Corp. plans to begin full-scale mass production of its Sphelar spherical micro solar cell at its Eniwa Operation in Eniwa City, Hokkaido, Japan.
While existing planar solar cells can take light only from their elevation surface, the Sphelar cell allows light to reach its cells from all directions because it has a spherical surface, providing a high level of photoelectric conversion efficiency. [...]
The company uses conditions of microgravity to form the Sphelar cells from molten silicon. Surface tension causes the silicon to take on a nearly perfect spherical shape. Due to segregation effects gained during the solidification process, single crystal silicon with a purity of 99.9999 percent can be obtained. The pn junctions are created using an n-plus diffusion process. Silver paste is used to attach electrodes. The product is finished with a coat of reflection film. [...]
If a Sphelar cell is encapsulated in acrylic resin, it can be turned into Flexible Sphelar sheet, a thin solar cell module whose shape can flexibly be changed into, say, a crescent or a curved form.
A module made with a series of Sphelar cells connected in parallel on silicone resin achieves a photo electric conversion efficiency of 19 percent.

See also this earlier article (”Spherical Solar Cells Solve Issue of 3-D Sunlight Reception”, 2003).