A room temperature ionic liquid crystal, 1-dodecyl-3-ethylimidazolium iodide （C12EImI）, and an ionic liquid, 1-decyl-3- ethylimidazolium iodide （Cl0EImI）, have been synthesized, characterized and employed as the electrolyte for dye-sensitized solar cells （DSSC）. The physicochemical properties show that a smectic A （SmA） phase with a lamellar structure is formed in CIzEImI. Both C^2EImI and Cl0EImI have good electrochemical and thermal stability facilitating their use in DSSC. The steady-state voltammograms reveal that the diffusion coefficient of I3- in C^2EImI is larger than that in CmEImI, which is at- tributed to the existence of the SmA phase in Ca2EImI. Because the iodide species are located between the layers of imidazo- lium cations in CjzEImI, exchange reaction-based diffusion is increased with a consequent increase in, the overall diffusion. The electrochemical impedance spectrum reveals that charge recombination at the dyed TiOJelectrolyte interface of a C12EImI-based DSSC is reduced due to the increase in I3- diffusion, resulting in higher open-circuit voltage. Moreover, both short-circuit current density and fill factor of the Cl2EImI based DSSC increase, as a result of the increasing transport of I3 in C^2EImI. Consequently, the photoelectric conversion efficiency of C^2EImI-based DSSC is higher than that of the Cl0EImI-based DSSC.
PAN XuWANG MengFANG XiaQingZHANG ChangNengHUO ZhiPengDAI SongYuan
A low molecular mass organogelator(LMOG),N,N’-1,5-pentanediylbis-dodecanamide, was applied to quasi-solid-state dye-sensitized solar cells(QS-DSSCs). The crosslinked gel network was self-assemblied by the LOMG in the liquid electrolyte, and the in situ assembly process of gelator can be obtained by the polarized optical microscopy(POM). On one hand, the network hinders the diffusion of redox species and accelerates the electron recombination at the interface of the TiO_2 photoanode/electrolyte. On the other hand, Li+ can interact with the amide carbonyl groups of the gelators and the adsorption of Li+ onto the TiO_2 surface decreases, leading to a negative shift of the TiO_2 conduction band edge, accelerated electron transport and decreased electron injection efficiency(η_(inj)) of QS-DSSC. As a result, the incidental photon-to-electron conversion efficiency(IPCE),the short circuit photocurrent density(J_(sc)) and the open circuit voltage(V_(oc)) of the QS-DSSC are decreased compared with those of the liquid electrolyte based DSSC(L-DSSC),which indicates that the electron recombination plays a great role in the photovoltaic performances of DSSC. Remarkably,the QS-DSSC exhibits excellent thermal and light-soaking stabilities during accelerated aging tests for 1000 h, which is attributed to a great intrinsic stability of the gel electrolyte with a high gel to solution transition temperature(T_(gel)=108°C).
A novel supramolecular gel electrolyte formed from two-component low molecular mass organogelators was developed and introduced into quasi-solid-state dye sensitized solar cell(QS-DSSC). This supramolecular gel electrolyte system was prepared by using N,N?-1,5-pentanediylbis-dodecanamide and 4-(Boc-aminomethyl)pyridine as co-gelator. Furthermore, the morphologies of the two-component supramolecular gel electrolyte and single-component gel electrolyte were observed by the polarized optical light microscopy, and the charge transport property of the two-component supramolecular gel electrolyte and the kinetic processes of the electron transport/recombination were investigated by the intensity-modulated photocurrent spectroscopy/intensity-modulated photovoltage spectroscopy(IMPS/IMVS). The polarized optical microscopy(POM) revealed that the single-component gel electrolyte was formed as the rod-like fibers, whereas the fibers changed to branched structure in the two-component supramolecular gel electrolyte. Moreover, comparing with the single-component gel electrolyte based QS-DSSC, the electron transport is faster and the electron recombination at the Ti O2/electrolyte interface is slower in the two-component supramolecular gel electrolyte based QSDSSC. Consequently, an efficiency of 7.04% was obtained by the two-component supramolecular gel electrolyte based QSDSSC, which is higher than that of the single-component gel electrolyte based QS-DSSC(6.59%).
