Preparation Of Novel Quasi-Solid-State Electrolyte Without Iodine And Its Application In Dye-Sensitized Solar Cells

Due to its low-cost and high efficiency, dye-sensitized solar cells (DSSCs) have been the most promising candidate for traditional silicon solar cells since it was first invented in1991. However, traditional organic liquid electrolytes composed of I-/I3-redox couple are volatile, poisonous, corrosive and with optical absorption, which hurdles the encapsulation of DSSC and limits its industrialization. Thus, we carried out iodine free quasi solid-state electrolytes based on different matrix, and broadened spectral response of photoanodes. The main contents and conclusions are as follows:1. CuI gel electrolyte is prepared by employing CuI as hole transport material, PEO as gelator and LiC104as dopant. It is concluded that PEO can inhibit the crystallization of Cul, promoting well interfacial contact between TiO2/CuI. Cul gel electrolyte doped with3wt%LiClO4achieves the highest ionic conductivity of8.7×10-3S cm-1. With LiClO4doped, PEO can be transformed to highly amorphous matrix. In addition, Li+absorbed on TiO2would enhance the electron injection efficiency. With PEO and LiC104participated Cul electrolyte, DSSC achieves an overall efficiency of2.81%, showing a96-116%improvement. The above Cul gel electrolyte is proved to be low cost, simple and eco-friendly, which offers us novel hole transport material for solid-state DSSC.2. Ionic liquid gel electrolyte is prepared by employing1,2-dimethyl-3-propyl imidazolium iodide (DMPII) as charge transfer intermediate, PEO as gelator and KI as charge transfer enhancer. With KI participation, ionic conductivity goes up to16.32×10-3S cm-1. The existance of K+in electrolyte can inhibit the crystallization of PEO, and promote electron transfer between TiO2/dye/electrolyte. Compared to the DSSC based on ionic liquid electrolyte without KI (4.05%),5wt%KI doped electrolyte based DSSC obtains an improvement of45%, with Jsc of14.11mA cm-2, Voc of0.71∨and η of5.87%, respectively. Due to the advantages of simple, highly efficient and eco-friendly, the above ionic liquid gel electrolyte provides reference for the development of quasi solid-state DSSCs.3. To improve the rheological behavior of ionic liquid electrolyte, binary ionic liquid electrolyte is prepared by employing BMII as charge transfer intermediate, LiTFSI as charge transfer enhancer and BMISCN with low viscosity as dopant. Ionic liquid BMII based DSSC without I2can work well and obtain a low efficiency of2.66%, addition of BMISCN can decrease the viscosity of electrolyte and improve the charge exchange reaction, leading to a higher efficiency of4.33%. LiTFSI doped with electrolyte could not only increase its ionic conductivity, but also improve the transportation of charge carrier and inhibit charge recombination in DSSC, finally yields the highest efficiency of5.55%, with an increasement of28%. I2is demonstrated to be unnecessary in the binary ionic liquid electrolyte. Since the bove binary ionic liquid electrolyte is proved to be simple, non-volatile and eco-friendly, it offers us novel suggestion for development of ionic liquid electrolytes.4. In order to overcome the flowability of ionic liquid electrolyte, plastic crystal ionic liquid electrolyte is prepared by employing BMII and PMII as charge transfer intermediate, succinonitrile as solid solvent. It is concluded that5wt%LiClO4doped in plastic crystal ionic liquid electrolyte could transform succinonitrile matrix into amorphous matrix, increase the ionic conductivity of electrolyte and promote the charge exchange reaction between I-and I3-through electrostatic attraction, therefore improves the efficiency of DSSC up to5.50%, revealing an improvement of157%compared to that of without LiC104doped. Attributing to its flexible, non volatile and eco-friendly, the above plastic crystal ionic liquid electrolyte is beneficial for the industrialization development of flexible and solid-state DSSCs.5. To demonstrate that iodine-free ionic liquid gel electrolyte is workable in cosensitized DSSC, we combined organic dye OD-8and D149or SQ2with complementary spectral response for stepwise cosensitization of photoanode, and assembled the quasi solid state DSSCs. It is hopeful to take advantage of OD-8and D149or SQ2’s complementary spectral response to increase the light harvesting efficiency of DSSC. The overall efficiencies of OD-8/D149(6.21%) and OD-8/SQ2(6.10%) cosensitized DSSCs are superior to that of OD-8(4.53%), D149(5.46%) and SQ2(2.86%) sensitized DSSCs. In addition, iodine-free ionic liquid gel electrolyte can operate successfully in cosensitized DSSC, and achieves higher Jsc, Voc and r(than that of organic liquid electrolyte based DSSC, suggesting that iodine-free ionic liquid gel electrolyte is promising in cosensitized DSSC and provides us novel method for preparation of DSSCs with broad spectra response and eco-friendly.