These are non-silicon solar cells that store solar energy at the earth’s surface. Most solar cells today use silicon semiconductors, but the manufacturing process requires much energy and high costs. To resolve these issues, many universities and corporations in Japan are working on improvements. The current focus is on thin-film type cells, in which the semiconductors are thinner than silicon cells, and dye-sensitized solar cells, which accumulate solar energy at a higher rate. A characteristic of both types is their low cost.