Browsing by Author "Seidalilir, Zahra"

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High-Performance and Stable Gel-State Dye-Sensitized Solar Cells Using Anodic TiO2 Nanotube Arrays and Polymer-Based Gel Electrolytes
(2015-06-17)
Seidalilir, Zahra
;
Malekfar, Rasoul
;
Wu, Hui-Ping
;
Shiu, Jia-Wei
;
Diau, Eric Wei-Guang
Highly ordered and vertically oriented TiO2 nanotube (NT) arrays were synthesized with potentiostatic anodization of Ti foil and applied to fabricate gel-state dye-sensitized solar cells (DSSCs). The open structure of the TiO2 NT facilitates the infiltration of the gel-state electrolyte; their one-dimensional structural feature provides effective charge transport. TiO2 NTs of length L = 15-35 mu m were produced on anodization for periods of t = 5-15 h at a constant voltage of 60 V, and sensitized with N719 for photovoltaic characterization. A commercially available copolymer, poly(methyl methacrylate-co-ethyl acrylate) (PMMA-EA) served as a gelling agent to prepare a polymer-gel electrolyte (PGE) for DSSC applications. The PGE as prepared exhibited a maximum conductivity of 4.58 mS cm(-1) with PMMA-EA (7 wt %). The phase transition temperature (T-p) of the PGE containing PMMA-EA at varied concentrations was determined on the basis of the viscosities measured at varied temperatures. T-p increased with increasing concentration of PMMA-EA. An NT-DSSC with L = 30 mu m assembled using a PGE containing PMMA-EA (7 wt %) exhibited an overall power conversion efficiency (PCE) of 6.9%, which is comparable with that of a corresponding liquid-type device, PCE = 7.1%. Moreover, the gel-state NT-DSSC exhibited excellent thermal and light-soaking enduring stability: the best device retained similar to 90% of its initial efficiency after 1000 h under 1 sun of illumination at 50 degrees C, whereas its liquid-state counterpart decayed appreciably after light soaking for 500 h.
High-Performance Gel-Type Dye-Sensitized Solar Cells Using Poly (methyl methacrylate-co-ethylacrylate)-Based Polymer Gel Electrolyte with Superior Enduring Stability
(2015-01-01)
Seidalilir, Zahra
;
Malekfar, Rasoul
;
Shiu, Jia-Wei
;
Wu, Hui-Ping
;
Diau, Eric Wei-Guang
We fabricated high-performance gel-state dye-sensitized solar cells (DSSCs) using TiO2 nanoparticles (NPs) and one-dimensional TiO2 nanotube (NT) arrays as electrodes and a polymer gel electrolyte (PGE), poly(methyl methacrylate-co-ethyl acrylate) (PMMA-EA), as a gelator in 3-methoxypropionitrile (MPN). MPN instead of acetonitrile (ACN) was used as a solvent to prepare PGE to overcome the drawback of high volatility of ACN so as to improve the long-term stability of the devices. The viscosities of the PGEs containing varied concentrations of PMMA-EA copolymer (4-13 wt%) were measured to obtain the gel to liquid phase transition temperature (T-p) of the PGEs. T-p systematically increased with increasing concentration of PMMA-EA. We found that the as prepared PGE showed the best electrical conductivity of 1.6 mS cm(-1) at 10 wt% of PMMA-EA, which is comparable with the value of the liquid electrolyte (1.7 mS cm(-1)). By employing 10 wt% of PMMA-EA as POE in MPN, the gel-type NT and NP-based devices exhibited power conversion efficiencies (PCE) 6.3 and 8.4%, respectively, which are comparable to those of the corresponding liquid-type counterparts, PCE = 6.4 and 9.1%, respectively. In addition, the enduring stability of MPN-based gel-state device was found to retain a high device efficiency for a long period under thermal and light-soaking dual stress. (C) 2015 The Electrochemical Society. All rights reserved.