Scientists have successfully developed a Perovskite solar call containing Cesium which has attained an efficiency of 21.1%, as well as a world record for reproducibility. by Denis Meyer @ elektormagazine.com:
In adding Cesium, the scientists at EPFL, let by Michael Saliba, have developed the first Perovskite compound with triple cations (Cs/MA/FA). These new films are more stable in hot conditions and less affected by fluctuations in environmental variables. They have confirmed efficiencies of 21.1%, and exit efficiency of 18% in operational conditions, even beyond 250 h.
21.1% efficiency with Perovskite solar cells – [Link]