Effects of idling time between depositions of organic layers and metal electrode in organic photovoltaic device

Abstract Deposition of metal cathode in organic photovoltaic (OPV) devices is known to cause serious metal atom penetration into the active layers and as a remedy, exciton blocking layer (EBL) is implemented. It is found that the metal penetration through EBL can be controlled by optimizing the idling time between the depositions of EBL and cathode layers. Both electrical and optical data show that the resistance of BPhen layer (EBL) to metal (Mg:Ag) penetration increase with increasing idling time. Also, significant variation in power conversion efficiency (PCE) is observed in subphthalocyanine chloride (SubPc)/fullerene (C60) based organic photovoltaic (OPV) cells by simply adding idling time as an additional control parameter. Device with optimized BPhen thickness and idling time resulted in a PCE of 2.8% whereas that of no idling time consideration has PCE limited at 2.3%. These observations are attributed to slow processes of self-organization in BPhen after their depositions.