CeO_<i>x</i>-Mesoporous Silica Nanoparticle Antioxidants to Enhance the Stability of Organic Photovoltaic Devices

Mitigating ultraviolet exposure-induced photodegradation remains a critical challenge to the long-term stability of organic photovoltaics (OPVs). Here, we improved the stability of the OPV device by introducing an antioxidant interlayer composed of nanocrystalline ceria supported on mesoporous silica nanoparticles (CeOx-MSN). The CeOx nanocrystals within the CeOx-MSN exhibited a high density of oxygen vacancies and a large ratio of Ce(III) chemical states known to scavenge reactive oxygen species. Optimizing the particle size of the CeOx nanocrystals further enhanced the ratio of Ce(III) states, enabling superior radical scavenging efficacy in methyl violet degradation tests compared with commercial CeOx nanostructures. The OPV performance test confirmed that the optimized CeOx-MSN (CeOx-MSN_S) can scavenge radicals without a degradation in initial performance under one-sun illumination. More importantly, the photostability test revealed that the OPV device with CeOx-MSN_S retained 73% of initial performance while the conventional device retained only 54%, corroborating the excellent radical scavenging efficacy of CeOx-MSN_S.