Metal halide perovskites are often made by mixing cations or halides with formamidinium (FAPbI3), to get high power-conversion efficiency in perovskite solar cells. But at the same time, the most stable phase of FAPbI3 is photoinactive, meaning that it does not react to light'the opposite of what a solar power harvester should do. In addition, solar cells made with FAPbI3 show long-term stability issues. Now, researchers led by Michael Grätzel and Anders Hafgeldt at EPFL, have developed a deposition method that overcomes the formamidinium issues while maintaining the high conversion of perovskite solar cells.
In the new method, the materials are first treated with a vapor of methylammonium thiocyanate (MASCN) or formamidinium thiocyanate FASCN. This innovative tweak turns the photoinactive FAPbI3 perovskite films to the desired photosensitive ones.
