UV-cross-linked block copolymers for initiator-free, controlled in situ gelation of electrolytes in dye-sensitized solar cells

Abstract

In this work, a block copolymer as an initiator- and monomer-free UV-cross-linked component for the controlled in situ gelation of electrolytes in dye-sensitized solar cells (DSSCs) is proposed. This block copolymer consists of one block of p-hydroxystyrene units and the other block with poly(ethylene oxide-co-propylene oxide) side chains. This block copolymer is successfully prepared by means of nitroxide-mediated polymerization, imidization reactions and successive hydrolysis reactions. When a homogeneous mixture of this copolymer and a typical liquid electrolyte (LE) is irradiated with UV, the cross-linking is efficient and controlled. The electrolyte in the DSSCs transforms in situ to a gel polymer electrolyte when exposed to UV, affording DSSCs with a relatively high initial solar-to-electricity energy conversion efficiency (η) and improved long-term stability that is significantly greater than that of the DSSCs with LE. These results demonstrate that the electrolyte system containing the UV-cross-linked block copolymer improves the long-term performance of DSSCs and contributes to the development of efficient and stable DSSCs.