A Porphyrin-Fullerene Dyad with a Supramolecular 'Double-Cable' Structure as a Novel Electron Acceptor for Bulk Heterojunction Polymer Solar Cells

摘要

Bulk heterojunction (BHJ) polymer solar cells (PSCs) offer a promising, low-cost, large-area, flexible, light-weight, clean, and quiet alternative energy source for both indoor and out door applications.[1-4] Power conversion efficiencies (PCEs) in response to solar AM1.5 radiation as high as 6-8% have been reported for BHJ PSCs.[5,6] In order to achieve PCEs over 10%, BHJ materials capable of generating higher short circuit cur rent (J_sc) and larger open circuit voltage (V_oc) are required.[7,8] One approach to increase J_sc and V_oc is to develop low-bandgap semiconducting polymers with deeper HOMO (highest occu pied molecular orbital) energies.[9-12] An alternative approach is to develop new electron acceptors with higher LUMO (lowest unoccupied molecular orbital) energies.[13-15] The pathway to low-bandgap semiconducting polymers with deeper HOMOs is now well established, and BHJ PSCs fabricated using these novel semiconducting polymers have demonstrated high PCEs.[5-12] On the other hand, the development of novel elec tron acceptors is behind the pace of the progress of develop ment of PSCs. The synthesis of novel electronic acceptors with controlled molecular electronic structures and solid-state supramolecular structures is urgently required, among which a supramolecular "double-cable" structure consisiting of two separated channels for charge transport is particularly desirable in generating high J_sc and thus, higher PCEs.[13-16]