The Study Of Polymer Gel Electrolytes Based On1-vinylimidazole For Dye-sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) have attracted large attention due to easy fabrication, low cost and high conversion efficiency. Electrolytes play an important role in the photovoltaic performances of the DSSCs. Now many studies are focused on solid and quasi-solid electrolytes with excellent thermal stability because the leakage and the volatilization of liquid electrolytes hinder their practical applications.In this paper, two different species of copolymers based on1-vinylimidazole (VIM) were synthesized and successfully implemented to formulated novel gel polymer electrolytes (GPE) for dye-sensitived solar cells. The studies were as followed.Firstly, P(VIM-MMA-MAA)/PEG400was used to form quasi-solid gel electrolyte. The solar cells based on P(VIM-MMA-MAA)/PEG400/LiI/I2/GBL were fabricated. The optimal component of GPE was as followed:15wt%P (VIM-MMA-MAA)/PEG400,0.1mol/L LiI and0.05mol/L I2. The ionic conductivity (σ) was5.01mS/cm and the η of the DSSC was3.39%(0.16cm2, AMI.5,100mW/cm2), which was similar to DSSC based on liquid electrolyte(η=3.40%). The effects of carboxyl group content on the cells’performances were studied. Three different additives were added to the electrolyte. It was found that TBP, P Y as well as VIM improved the efficiency of DSSCs.The hydrogen bonds of polymer gel electrolyte were analyzed by IR. SEM was used to characterize morphology of gel electrolyte. It was found that the stability of gel electrolyte was better than that of liquid electrolyte by TG analysis. EIS results showed electrolyte with more MAA and less PEG400had smaller impedance.In the second part, poly(vinyidene fluoride-co-hexafluoro propylene)(P(VDF-HFP)) was introduced to the polymer to improve the effect of solidifying standard liquid electrolyte. A novel gel polymer electrolyte was prepared with P(VIM-MMA)/P(VDF-HFP). The solvent was3-methoxypropionitrile. DSSCs based on P (VIM-MMA)/P(VDF-HFP)/LiI/I2/3-MPN were tested. The maximum energy conversion efficiency (η) of DSSC reached4.74%(0.16cm2, AM1.5,100mW/cm2).η of DSSC based on liquid electrolyte was5.38%. The additives of TBP, PY and GuSCN were added to the electrolyte. They had different effects on the DSSCs baesd on P (VIM-MMA)/P(VDF-HFP)(15w)/LiI/I2. TBP and PY had a negative effect while GuSCN improved η. It was found effects of VIM with different concentrations on the DSSCs were different. When VIM was0-1mol/L, the figure between η and VIM for liquid system had a single peak while that of gel electrolyte was polygonal line.TG analysis indicated that the stability of gel electrolyte was better than that of liquid electrolyte. EIS results showed the component of gel electrolyte had effects on Pt/electrolyte interface impedance. TBP had suppression on dark reaction.All the blends were characterized by NMR and IR. The photovoltaic performances of DSSC were tested with solar photovoltaic system. The incident photon-current conversion efficiency (IPCE) was analyzed and results showed the addition of polymer had little effect on it.