Flexible perovskite solar cells (f-PSC) are excellent candidates for space applications, thanks to record efficiencies of 23.4% [1], close to the 26.1% record reached by rigid devices [2], and excellent power densities as high as 30.3 W/g [3].

Our previous work in Hole Transport Material (HTM) optimization revealed the positive impact of the insertion of benzothiadiazole (BTD) unit on a P3HT scaffold upon neutron irradiation [4]. Here we synthesized two different HTMs in which PTAA is copolymerized with (i) a phenothiazine or (ii) both a phenothiazine and a BTD. As an added value, the new HTMs could be processed in more sustainable solvents than toluene, i.e. THF.

Neutrons have shown to induce degradation in the performance of traditional solar cells used in space, however the literature on the matter for PSC is still not as extensive. Studying potential damage sources selectively will help us estimate more accurately the ageing of our devices in space. Therefore here we studied degradation damages induced by atmospheric-like neutrons (fluence of 5*109 n/cm2), provided by the Chip-IR beamline in the Rutherford Appleton laboratory, which well represent the environment in Low Earth Orbit [5]. PV characterization of the devices showed that the new HTMs (and especially the BTD-modified one) are a viable alternative to the commercially available PTAA, with improved resilience to atmospheric neutrons. Furthermore, photoluminescence imaging revealed negligible damage in the active perovskite itself, suggesting that the loss in electrical performance is attributable to charge extraction processes and interface degradation.

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