Perovskites in Space: Promising Results Aboard Two ISS Missions

The rapid commercialization of low Earth orbit (LEO) and NASA’s return to the moon will require next-generation photovoltaic materials with high specific power and defect tolerance. Perovskite solar cells (PSCs) are an excellent candidate for such missions, having demonstrated their resilience against the unique stressors of space. These include rapid temperature cycling with each orbit, high-energy particle radiation, increased ultraviolet light in the AM0 spectrum, and exposure to atomic oxygen. This work discusses the effects of LEO on metal halide perovskite (MHP) samples from two recent Materials International Space Station Experiment (MISSE) missions. MISSE-15, launched in 2021, included eight PSCs of varying architecture and absorber composition to test several prototype devices. The cells were placed in open circuit at zenith orientation (facing normal away from the Earth) outside the ISS for 6 months before returning to Earth for characterization. MISSE-16 included five encapsulated methylammonium lead iodide (MAPI) thin films with different cover glass layers to test the effects of UV radiation. Upon return, all samples were investigated with high-resolution spectroscopy and microscopy. Photoluminescent (PL) emission and recombination lifetime data from the MISSE samples were compared with control devices to quantify how the former changed under LEO conditions.<br/><br/>Ultimately, all MHP samples showed strong PL emission intensity and little sign of chemical degradation. MISSE-16 films were encapsulated with long pass and band pass UV filters instead of standard top glass to expose each sample to specific UV wavelengths. This test was designed to study if and how MHPs would be affected by various UV bands in combination with the space stressors previously described. All five samples exceeded expectations, returning uniform, emissive, and energetically stable. Of the eight PSCs aboard MISSE-15, only the two CsPbI₂Br cells experienced absorber failure. These cells returned nearly transparent due to CsPbI₂Br photobleaching. The remaining six PSCs, including two each of MAPI, triple cation, and formamidinium-rich triple cation cells, returned with their absorber layers intact. Unfortunately, all cells experienced degradation to their top electrodes (Al or Ag depending on PSC), resulting in no electrical response in post-flight tests. This appears to be caused by ion migration, likely iodide, between the MHP and the metal. However, all MHP films were stable and emissive in regions without contacts and only slightly altered in areas behind the damaged contacts, further confirming the resilience of MHPs. Future MISSE missions will soon launch containing PSCs with indium tin oxide and Au contacts which are known to prevent ion transfer. Overall, the high stability and PL response of MHP films and cells demonstrates their ability to withstand the harsh environment of space.<br/><br/>*This work was supported by NASA grant no. NNH18ZHA008CMIROG6R and NSF grant no. NSFDGE-2125510.