Enhanced Photo-Stability of Printable Organic Photovoltaics Based on Non-Fullerene Acceptors

Abstract

With emergence of the non-fullerene acceptors (NFAs), organic photovoltaics (OPVs) have been developed rapidly achieving unprecedented power conversion efficiencies (PCEs) of 15.7 % for single junction cells and 17.3 % for tandem cells. However, despite of these prodigious progress of OPVs, there are still many challenges remained should be resolved to push the OPV technology further into real-life application. Especially, studies on photo-stability of OPVs are essential, but have not been reported much. Here we investigated the possible origins of the poor stability of OPVs in inverted architecture using ITIC-based NFAs. To extend the lifetime of NFA-based OPVs further, we applied two systematic approaches: modifying the end groups of NFAs (molecular engineering), and introducing a new cathode interlayer to replace ZnO which have photocatalytic activity (interface engineering). Using NFAs with modified end groups, we have extended the lifetime of OPVs more than 6 times. In addition, by replacing ZnO with C60-SB/PFN-Br as a new cathode interlayer, we dramatically enhanced the photo-stability of OPVs. From this works, we hope our findings propose specific directions for more systematic stability studies.