Hydroxyl Silicone-modified Polyurethane-based Gel Electrolyte For DSSCs

Dye-sensitized solar cell (DSSC), as a new generation of solar cells has been attracted considerable attention in recent years because of its high efficiency, low cost, and simple manufacturing process. DSSC is composed of a nanocrystalline TiO2 film anode, sensitizing dye, an electrolyte and the Pt electrode.Wherein the electrolyte is an important part of the DSSC, which plays the role of regeneration of dye and electrons transporting. In particular gel electrolyte has been attracted worldwide attention of the researchers due to its stability and the higher conductivity.This paper studied a class of in-situ polymerization polyurethane (PU) gel electrolyte systems which was modified by silicone and added some nitrogen-containing heterocycles as additives. Based on this type PU gel electrolyte, the conductivity of the electrolyte was promoted, the gelation time can be controlled, and the photoelectrical conversion efficiency of the DSSCs assembled significantly increased.During the preparation of silicone modified polyurethane electrolyte, the influences of the molecular weight of PEG, the structure and content of silicone oil, the type of the solvent, iodized salt, concentration of NaI/I2. the content of the electrolyte added on the conductivity were studied. It has been shown that the highest conductivity 7.13mS.cm-1 was achieved when the hydroxyl molar ration of PEG 10000 and hydroxy silicone oil DMS-CA21 was 1:1,1,4-butyrolactone was used as solvent, concentration of NaI/I2 was 0.5/0.05mol.L-1. The composition of PU electrolyte was characterized by FT-IR, and the structural analysis and thermal stability of electrolytes were characterized by SEM and DSC. The photoelectric conversion efficiency of the DSSC in situ assembled based on the optimized PU gel electrolyte was reached 4.85% under the illumination of 100mW/cm2. The SEM and EIS analysis showed that the flexibility of PU molecular chain increased was advantageous to increase the infiltration of TiO2 electrode and reduce the impedance of the contact interface.A series different nitrogen-containing heterocyclic compound gel electrolytes were prepared with pyridine or imidazole compound as additives. It was found that when 0.3mol/L pyridine(PY) or 4-tert-butyl pyridine (4-TBP) was added into the precursor solution composed of TDI and PEG 10000, hydroxyl silicone oil DBE-C25, including 0.5/0.05 mol. L-1 NaI/I2,1,4-butyrolactone as solvent, the gelation time of the electrolyte can be controlled at about 110 min or 90 min.Compared with the electrolyte without nitrogen-containing heterocyclic compound as additives, the gelation time shortened, and the conductivity did not changed. The photoelectric conversion efficiency of DSSC based on the gel electrolyte reached 6.53% under the illumination of 100mW/cm, an improvement of 48.7% than that without adding nitrogen heterocyclic compound.