Proton Radiation Hardness of Organic Photovoltaics

Recent developments of solution-processed bulk-heterojunction organic photovoltaic<br/>(OPV) cells have demonstrated power conversion efficiencies (PCEs) as<br/>high as 18.7% for single-junction devices. Such a high PCE in addition to its<br/>desirable lightweight property and high mechanical flexibility can realize high<br/>specific power and small stowed volume, which are key considerations when<br/>choosing PV for space missions. To take one important step forward, their<br/>resilience to ionizing radiation should be well studied. Herein, the effect of proton<br/>irradiation at various fluences on the performance of benchmark OPV cells is<br/>explored under AM0 illumination. The remaining device performance is found to<br/>decrease with increasing proton fluence, which correlates to changes in electrical<br/>and chemical properties of the active layer. By redissolving the devices, the<br/>solubility of the active layer is found to decrease with increasing proton fluence,<br/>suggesting that the active materials are likely cross-linked. Additionally, Raman<br/>studies reveal conformational changes of the polymer leading to a higher degree<br/>of energetic disorder. Despite a drop in performance, the retaining percentage of<br/>the performance is indeed higher than the current market-dominating space PV<br/>technology—III–V semiconductor-based PV, demonstrating a high potential of<br/>the OPV cell as a candidate for space applications.