Well-connected TiO2 nanocrystals via solid-state reaction for dye-sensitized solar cells. (10th September 2015)

• Record Type: Journal Article
• Authors: Zhang, Jie; Rui, Yichuan; Li, Yaogang; Zhang, Qinghong; Wang, Hongzhi
• Is Part Of: Electrochimica acta. Volume 176(2015)
• Page Start: 480
• Page End: 487
• Publication Date: 2015-09-10
• Subjects: Well-connected TiO2 nanocrystals -- solid-state reaction -- dye-sensitized solar cells -- photoanode -- electrochemical impedance spectroscopy; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2015.07.041
• Languages: English
• ISSNs: 0013-4686

Abstract

Graphical abstract: Well connected anatase TiO2 nanocrystals were synthesized by solid state reaction, which had a lower resistance and their DSSCs gained an efficiency as high as 8.16 %. Highlights: An alternative way to fabricate TiO2 nanocrystals for DSSC photoanode via solid state reaction was presented. The DSSC with an efficiency of 8.16 % was archived by TiO2 well-connected nanocrystals resulted from the decomposition of (NH4 )2 TiO(SO4 )2 . EIS indicated the well connected TiO2 nanocrystals in DSSCs had a lower resistance. Abstract: TiO2 nanocrystals derived from hydrothermal method were widely used as the photoanodes of dye-sensitized solar cells (DSSCs). Developing some alternative routes combining low-cost with high performance is eagerly expected. Well connected anatase TiO2 nanocrystals were synthesized by one-step thermal decomposition of the double salt (NH4 )2 TiO(SO4 )2 (ammonium titanyl sulfate, ATS) at 700 °C for 2 h, and the fine tuning on aggregate sizes was achieved by adjusting the heating rate. The TiO2 nanocrystals inside the aggregates were densely packed where each nanocrystal contacted well to neighbouring grains. The connected structure between the crystallites decreases the negative effects of electron grain boundary crossing and reduces recombination within the aggregate when used as photoelectrodes of dye-sensitized solar cells. Moreover, TiO2 aggregates from ATS calcined at a faster heating rate (5 °C/min) had a wider pore size distribution and exhibited a higher light scattering abilities, while the ones from those calcined at a slower heating rate (3 °C/min) had a narrow pore size distribution but possessed a higher specific surface area (72.8 m 2 g −1 ) for adsorbing more dye. The DSSC based on two kind of TiO2 nanoparticles as the photoelectrode all exhibited an excellent short-circuit current density (15.21 mA cm −2 and 15.94 mA cm −2 ) and a highly efficient power conversion efficiency (7.78% and 8.16%). The improvements of power conversion efficiency for two kinds of TiO2 nanoparticles compared to commercial Aerosil process P25 nanoparticles are mainly attributed to a higher light scattering ability and superior dye adsorption property, respectively. The electrochemical impedance spectroscopy (EIS) analysis indicated the DSSCs with TiO2 nanocrystals derived from solid state reaction had a lower charge transfer resistance than all P25 photoanodes at TiO2 /dye/electrolyte interface due to the well connected structure provided multiple contacts to neighboring grains.