A team of Swiss, Chinese and Japanese researchers has found a way to scale up perovskite solar cells without a loss of stability. Instead of changing the perovskite, the researchers added a new element to the device, a thin film light collector that is placed over the cells.

The film was constructed in two layers, one a positively charged cubic rocksalt semiconductor, the other a sheet of negatively charged titanium oxide. Arriving light causes the perovskite layer to be excited, which results in freed electrons moving through the titanium oxide layer on one side of the film while holes are transported through the other. The result is a protective film covering that actually increases conductivity of the device.

In addition to allowing perovskite based devices to be scaled up, the film also boosted efficiency—to levels slightly higher than 15%. The film was also found to protect the cells from humidity, which is usually an additional factor holding back the development of perovskite based cells that can be used in the real world.