Neutron irradiated perovskite films and solar cells on PET substrates

Flexible perovskite solar cells feature high power-per-weight ratio and low cost manufacturing, which make them very attractive for space and avionic applications. It is thus paramount to assess their response to the harsh space environment. Although an increasing number of studies have been investigating the effect of electron and proton radiation on perovskite solar cells, very few have dealt with neutron irradiation and even less with flexible devices. In this paper, the stability of unencapsulated flexible perovskite solar cells against fast neutron irradiation at two different fluence levels is evaluated, comparing commercially available spiro-OMeTAD and an in-house modified P3HT as the hole transport materials. We observed degradation for both materials and at both fluences. Modified-P3HT cells experienced remarkable smaller voltage and current losses compared to spiro-OMeTAD; still, their overall performance degraded similarly to spiro-OMeTAD devices at higher fluence, whilst it suffered a much higher drop than spiro-OMeTAD at lower fluence, as a consequence of a larger decrease in fill factor, ascribable to a sub-optimal perovskite/polymer interface. Spectral response and behavior at different light intensities of modified-P3HT cells suggest the polymer to be potentially more resilient than spiro-OMeTAD under fast neutron irradiation, once the perovskite/polymer is improved, although further investigations are needed to gain more insights and push the development and adoption of flexible PSCs for space and avionic applications.