A Novel Thermosetting Gel Electrolyte for Stable Quasi‐Solid‐State Dye‐Sensitized Solar Cells

Abstract

Since the prototype of a dye-sensitized solar cell (DSSC) was reported in 1991 by O'Regan and Grätzel, [1] it has aroused intensive interest over the past decade due to its low cost and simple preparation procedure. [1,2] Based on liquid electrolytes, a photoelectric conversion efficiency of 11 % for DSSC has been achieved. [3,4] However, the potential problems caused by the liquid electrolytes, such as the leakage and volatilization of liquid, is considered as some of the critical factors limiting the long-term performance and practical use of the DSSCs. Thus, solid-state and quasi-solid-state electrolytes, such as polymer gel electrolytes, organic hole conductors and inorganic p-type semiconductors, [5][6][7][8][9][10][11][12][13][14][15][16][17] were attempted to replace the liquid electrolytes. However, due to low ionic conductivity, imperfect soakage of porous TiO 2 film and poor contact with counter electrode, the photoelectric conversion efficiency of DSSCs based on the solid-state electrolytes were less than 5 %. If an electrolyte can avoid the leakage and volatilization of liquid electrolyte and keep a high ionic conductivity and good interface contact with porous TiO 2 film and counter electrode, it is possible to accelerate the practical application of DSSCs. Gel electrolyte is one kind of electrolyte according with the above prerequisites, especially these thermo-irreversible (Thermosetting) gel electrolytes, which show high ionic conductivity, perfect interface contact, excellent chemical stability and temperature tolerance. [6,8,[18][19][20][21] Here, we report a novel thermosetting gel electrolyte (TSGE) based on poly (acrylic acid)-(ethylene glycol) (PAA-PEG) hybrid absorbing liquid electrolyte. It is known that poly (acrylic acid) (PAA) is a superabsorbent with 3D networks structure and hydrophilic groups, it can absorb large amount of liquid and the absorbed liquid is hard to be released even under some pressure. [22,23] However, pure PAA is not a good absorbent for conventional organic solvents used in liquid electrolytes. By modifying with amphiphilic poly (ethylene glycol) (PEG), the PAA-PEG hybrid shows a high absorbent ability for liquid electrolytes and the absorbed liquid electrolytes are hard to be leaked and volatilized for a long time. On the other hand, due to large amount of liquid is contained in the PAA-PEG hybrid, the ionic conductivity and interface soakage ability of the PAA-PEG hybrid is superior to that of solid-state electrolyte or other polymer gel electrolyte. The absorbed liquid electrolyte is kept in the networks of the hybrid due to hydrogen bonding between carboxylic groups and ether groups in the hybrid. Moreover, through reaction between Lewis basic organic solvents and the polyacid hybrid (PAA-PAG), a part of solvents is hanging on the polymer chains. Consequently, an electrolyte with thermosetting character and good stability, and with advantages for both liquid electrolyte and solid state electrolyte can be expected. Based on the TSGE, the DSSC shows a high photoel...

Effect of the self-assembled gel network formed from a low molecular mass organogelator on the electron kinetics in quasi-solid-state dye-sensitized solar cells

“…Remarkably, the gel electrolytes formed from the LMOGs exhibit three dimensional networks and possess higher ionic conductivity, good pore filling and penetration of the mesoporous TiO2 film [21,22]. Importantly, the devices assembled by LMOGs exhibit good long-term stability because of a high gel to solution transition temperature of LMOGs [23,24].…”

Low temperature fabrication of high performance and transparent Pt counter electrodes for use in flexible dye-sensitized solar cells

“…The TiO 2 colloid was coated onto the Ti foil using a doctor-scraping technique. The thickness of the TiO 2 film was controlled by the thickness of the adhesive tape around the edge of the cleaned Ti foil [19][20][21]. After drying at room temperature, the TiO 2 thin films were sintered at 450°C for 30 min in air to give nanocrystalline TiO 2 films.…”

Preparation of porous nanoparticle TiO2 films for flexible dye-sensitized solar cells

“…The process was repeated for three times to form a thick TiO 2 film. The thickness of the TiO 2 nanocrystalline film was controlled by the thickness of adhesive tape around the edge of the cleaned ITO/PEN substrate [13,14]. The film was dried in moisture-free air and was irradiated with a ultraviolet light for a given time [8,15,16], the coated substrate was immersed in a 2.5×10 −4 mol/L ethanol solution of N719 for 24 h to adequately absorb the dye.…”