Perovskite solar cells (PSCs) have been getting significant attention in the photovoltaic community because of their high power conversion efficiency, solution processability, large-area device fabrication, and low production cost [1-3]. Recently, PSC technology is being studied for space applications to overcome its disadvantages in instability in normal terrestrial ambient air conditions containing moisture and oxygen [4]. The superiors combining with their high specific power (power per weight) [5] as well as the facile low-temperature solution processibility for in-situ fabrication in spaceships make PSCs a promising replacement for currently used PV technologies in space applications. However, the space radiation hardness of PSCs should be further studied before they can be applied in space missions.

In this work, PSCs were tested under 10MeV proton radiating from back side of the cells at different fluence of 10¹², 10¹³, 10¹⁴ proton/cm² which equivalents to 1, 10, and 100 years in medium Earth orbit [6]. With >24% initial efficiency of PSCs, this study accurately reflects the behaviour of fresh and state-of-the-art perovskites under proton radiations comparing to far lower initial efficiency in the previous reports. This is important as it isolates the proton-induced degradation of the studying PSCs from storage degradation and high density of existing defects in low efficiency PSCs. Therefore, we could confidently conclude that this experiment shows a high hardness of PSCs under 10MeV proton radiations, in which the samples stand at its ~90% initial efficiency at the highest fluence without any shielding. In terms of radiation-induced additional defect, ToF-SIMS analysis shows movement of gold and lead atoms into further layers after reacting with radiating protons. Additionally, SEM observations witness mechanical damage on surface of perovskite films when exposing proton radiation. These findings are visual evidence of proton-induced damages on materials during radiation. Besides, CL measurement at high resolution SEM images points out that the effect of radiations onto perovskite are uneven among grain and grain boundaries, indicating that there should be different kinds of defects were created during the radiation processes. Finally, the PL and TRPL show that the perovskite quality degrades a lot after being radiated at high fluence of proton. This is consistent with the reduction of Voc and FF observed during J-V characterization while there is a slight drop in terms of Jsc.

Overall, this is the first findings on mechanical interaction between protons and perovskite materials, in which PSCs were subjected to irradiation from the back side. With different fluences of 10MeV proton, PSCs show extremely high tolerance without any shielding, in which the PSCs can stand at its 90% initial efficiency at a fluence equivalents to 100 years in the medium Earth orbit.