Needle-like microstructure and device having needle-like microstructure

A photoelectric conversion device comprising:

• a first crystalline silicon region having a first conductivity type over a first conductive layer;
• a second crystalline silicon region comprising a plurality of whiskers over the first crystalline silicon region;
• a third crystalline silicon region having a second conductivity type over the second crystalline silicon region;
• and
• a second conductive layer over the third crystalline silicon region,
• wherein a whisker which is selected from the plurality of whiskers has a needle-like shape,
• wherein the whisker comprises a polycrystalline silicon,
• wherein the whisker has a growth direction, and
• wherein the whisker includes a twin crystal including a {111} plane as a twin boundary.

A secondary battery comprising:

• a negative electrode active material layer comprising a crystalline silicon
• including a plurality of whiskers over a negative electrode current collector;
• a separator over the negative electrode active material layer;
• a positive electrode active material layer over the separator;
• and
• a positive electrode current collector over the positive electrode active material layer,
• wherein a whisker selected from the plurality of whiskers has a needle-like shape,
• wherein the whisker comprises a polycrystalline silicon,
• wherein the whisker has a growth direction, and
• wherein the whisker includes a twin crystal including a {111} plane as a twin boundary.