High Performance Quasi-Solid-State Dye-Sensitized Solar Cells Based on Poly(lactic acid-co-glycolic acid)

Abstract

A stable quasi-solid-state dye-sensitized solar cell (DSC) with a novel amphiphilic polymer gel electrolyte (APGE) based on poly(lactic acid-co-glycolic acid) (PLGA) was fabricated. The APGE could be readily prepared by a simple one-pot synthesis at low temperature of 50 °C and exhibited a quasi-solid property, high conductivity, and long-term stability. The 20 and 40 wt% APGE-based DSCs show high photovoltaic conversion efficiencies of 7.5 and 7.4 %, respectively, under AM 1.5 simulated sunlight, which were comparable to the liquid electrolyte-based DSC with efficiency of 7.6%. The 40 wt% APGE-based DSC maintained 95% of the initial performance after 60 days in practical conditions. Subsequently, a completely different approach was taken to improve the performance of APGE-based DSCs without sacrificing long-term stability. For the purpose, light scattering submicron TiO2 particles were synthesized and incorporated into the APGE. Plenty of PLGA chains help a significant amount of the TiO2 particles well-disperse in the medium without precipitation as well as provide a large amount of “cages” for solvent molecules to be retained. The light scattering TiO2 particle-incorporated amphiphilic PGE (LS-APGE) enables complete light harvesting and long-term durability for qss-DSCs. Thus, LS-APGE-based DSCs show very high efficiencies of 8.2% exceeding liquid electrolyte-based cells (7.5%) and even those with conventional light scattering layers (7.8%). Also, no aggregation and precipitation of the light scattering particles occur during 60 days due to high polymer concentration (40 wt%) and their relatively large sizes (600~800nm).