Directed electron transfer in Langmuir-Schafer layers of porphyrin-fullerene and phthalocyanine-fullerene dyads in inverted organic solar cells

In this study double linked porphyrin-fullerene and phthalocyanine-fullerene dyads and a single linked phthalocyanine-fullerene dyad were studied as components in inverted organic solar cells (OSCs) equipped with the well known P3HT:PCBM bulk heterojunction as the photoactive layer. The dyad monolayers were deposited onto a surface of P3HT: PCBM by using the Langmuir-Schafer method, therefore forming oriented monolayers in which the electron donor (D) and the acceptor (A) exist as a close proximity pair in a 1 : 1 molar ratio. As a result of this structure short circuit current density (J(sc)), open circuit voltage (V-oc), and power conversion efficiency (eta) increased, while the fill factor (FF) remained the same. The devices which contained dyads with double linkage produced higher efficiencies than the one with a single linked dyad. This result can be explained in terms of molecular orientation. It was also verified that the prepared OSC devices have promising long term air stability.