An international research team, led by Stefan Weber from the Max Planck Institute for Polymer Research in Mainz, has found microscopic structures in perovskite crystals that can guide the charge transport in the solar cell.

Clever alignment of these electron highways could make perovskite solar cells more efficient. When solar cells convert sunlight into electricity, the electrons of the material inside the cell absorb the energy of the light. The electrons excited by the sunlight are collected by special contacts on the top and bottom of the cell. However, if the electrons remain in the material for too long, they can lose their energy again. To minimize losses, they should therefore reach the contacts as quickly as possible. Microscopically small structures in the perovskites - so-called ferroelastic twin domains - could be helpful in this respect: They can influence how fast the electrons move.

Researchers in the Cava Group at the Princeton University Department of Chemistry have lifted the mystery surrounding the reasons for instability in the inorganic perovskite cesium lead iodide (CsPbI₃), known for its potential in creating highly efficient solar cells.

Using single crystal X-ray diffraction performed at Princeton University and X-ray pair distribution function measurements performed at the Brookhaven National Laboratory, the Princeton researchers detected that the source of thermodynamic instability in the halide perovskite cesium lead iodide (CsPbI₃) is the inorganic cesium atom and its “rattling” behavior within the crystal structure.