Quasi-Solid-State Dye-Sensitized Solar Cells by Mechanically Stable Semi-Interpenetrating Network Polymer Gel Electrolytes for Indoor Applications

Herein, the copolymer composition of [AN] and [4VP] units of [P(AN-co-4VP)]₂-b-PEO (here, AN = acrylonitrile, 4VP = 4-vinylpyridine, and PEO = poly(ethylene oxide)) block copolymer (BCP) was controlled by reversible addition-fragmentation chain transfer (RAFT) polymerization to make it acetonitrile-soluble BCP so that this BCP can be further converted into in situ three-dimensional (3D) network polymer gel electrolytes (PGEs) inside the cell by quaternization reaction in acetonitrile-based liquid electrolyte media. Before in situ application, a fully semisolid 3D network polymer gel with high mechanical stability was obtained by optimizing the quaternization reaction conditions in an iodine liquid electrolyte medium. The excess cross-linking agent, 1,8-diiodooctane, was utilized to ensure a fully quasi-solid-state gel by chemical cross-linking in the presence of iodine and tert-butylpyridine (TBP) of the liquid electrolyte. The addition of liner PEGDME (average MW 2000) in a cross-linking polymer further enhances the mechanical stability of the network PGE. A remarkable photovoltaic performance, above 7% efficiency, was found for quasi-solid-state dye-sensitized solar cells (QSS-DSSCs) under 1 sun conditions, around 20% lower than that for volatile liquid-state DSSCs. However, the deviation of efficiency for QSS-DSSCs by using in situ 3D semi-IPN PGE was reduced to 10% with liquid-state DSSCs under compact fluorescent lamp (CFL) ambient light. 16-20% efficiency of QSS-DSSCs by in situ semi-IPN PGE under CFL light intensity of 200-2000 lx can be entirely satisfactory in terms of flexibility and mechanical stability of the device, which ensures the potential of these QSS devices to power indoor-placed wireless devices and low-powered consumer electronic devices.