Polymer nanofibers: preserving nanomorphology in ternary blend organic photovoltaics

The morphology of donor-acceptor blends holds the key to good performance through the balancing of good exciton dissociation efficiency and interconnectivity for good charge collection. In this work, the good morphology is preserved in ternary blend systems through the use of poly(3-hexylthiophene) (P3HT) nanofibers. The iridium(III)-based metal complex is incorporated in P3HT-PCBM blends as a triplet exciton sensitizer in the bulk heterojunction (BHJ) organic photovoltaics (OPV). The devices using triplet-sensitized ternary blends of P3HT experience a significant degradation in performance, a tendency further aggravated by thermal treatment. This is due to disruption in the morphology thus affecting charge generation and collection. In order to overcome these morphological issues and to circumvent the restriction due to the crystallization of the polymers, here we demonstrate the use of pre-assembled nanofibers in these ternary blends. The concept of stabilizing the nanomorphology of the blend material through the use of nanofibers can also be applied to other ternary systems.