Antioxidant Additive with a High Dielectric Constant for High Photo‐Oxidative Stabilization of Organic Solar Cells without Almost Sacrificing Initial High Efficiencies

Apart from power conversion efficiency (PCE) being the most important feature that requires improvement for organic solar cells (OSCs), their long‐term stability is another key factor for their successful commercialization. In fact, the lifetime of OSCs is severely limited by photoinduced oxidation, which occurs because of light radiation and the ingress of moisture (H 2 O) and oxygen (O 2 ) within an ambient atmosphere. Herein, dibutylhydroxytoluene (BHT)‐based nonvolatile antioxidant additives with polar cyanide (CN) and perfluorinated alkyl chains (designated as BHT–CN and BHT–PF) are developed, demonstrating that the OSCs will have significantly improved long‐term stability by using them when exposed to the combined action of all the aforementioned stresses. In particular, the use of BHT–PF in the various given test‐bed OSC systems can remarkably enhance the long‐term stability, as well as the high initial PCEs similar to the maximized values obtained from the highly optimized OSCs with each well‐known suitable solvent additive. The promising results are attributed to the simultaneously enhanced dielectric and radical scavenging properties induced by the BHT–PF embedded in the active‐layer matrices. Taking its easy applicability into consideration, the BHT–PF is very useful in fabricating OSC modules that should be stable under severe photo‐oxidation conditions.