The University of Tokyo announced Nov 29, 2017, that it has developed a semi-transparent perovskite solar cell with an energy conversion efficiency of 9.7%.

The university improved the transparency of the cell without lowering energy conversion efficiency. Specifically, by exploiting the fact that human vision is not very sensitive to blue (short-wavelength) or red (long-wavelength) light, the cell efficiently absorbs such light and converts it into energy.

This time, the university reduced the thickness of silver electrode to 10nm, which is more than 90% thinner than light wavelength, and the thickness of perovskite layer to 180nm. On the other hand, by introducing a silver nanocube with a side length of about 70nm to help absorb long-wavelength light, the loss caused by the thinner perovskite layer was compensated.