Topological insulators can be utilized in a new type of infrared photodetector that is intrinsically sensitive to the polarization of incident light and static magnetic fields. The detector isolates single topological insulator surfaces and allows light collection and exposure to static magnetic fields. The wavelength range of interest is between 750 nm and about 100 microns. This detector eliminates the need for external polarization selective optics. Polarization sensitive infrared photodetectors are useful for optoelectronics applications, such as light detection in environments with low visibility in the visible wavelength regime.

A solar cell includes a photoelectric converter having a p-type surface and an n-type surface on a principal surface, a p-side conductor, a p-side Sn layer, an n-side conductor, an n-side Sn layer, a p-side seed layer between the p-type surface and p-side conductor, an n-side seed layer between the n-type surface and n-side conductor, a p-side metal layer covering the p-side seed layer and including metal different from metal of the p-side seed layer, and an n-side metal layer covering the n-side seed layer and including metal different from metal of the n-side seed layer. The diffusion coefficient of copper with respect to the p-side metal layer is less than the diffusion coefficient of copper with respect to a p-side Sn layer. The diffusion coefficient of copper with respect to the n-side metal layer is less than the diffusion coefficient of copper with respect to an n-side Sn layer.

A solar cell includes a photoelectric converter having a p-type surface and an n-type surface on a principal surface, a p-side conductor, a p-side Sn layer, an n-side conductor, an n-side Sn layer, a p-side seed layer between the p-type surface and p-side conductor, an n-side seed layer between the n-type surface and n-side conductor, a p-side metal layer covering the p-side seed layer and including metal different from metal of the p-side seed layer, and an n-side metal layer covering the n-side seed layer and including metal different from metal of the n-side seed layer. The diffusion coefficient of copper with respect to the p-side metal layer is less than the diffusion coefficient of copper with respect to a p-side Sn layer. The diffusion coefficient of copper with respect to the n-side metal layer is less than the diffusion coefficient of copper with respect to an n-side Sn layer.