An enhanced degree of charge transfer in dye-sensitized solar cells with a ZnO-TiO2/N3/Ag structure as revealed by surface-enhanced Raman scattering.

A number of recent studies have focused on improving the performance of dye-sensitized solar cells (DSSCs). Cells with a ZnO-TiO2/N3/Ag structure have attracted particular attention because of their excellent power conversion efficiencies. Using a dendritic crystal ZnO-TiO2 composite semiconductor and Ag in conjunction leads to different charge-transfer (CT) processes, and this is the main theoretical basis for the improvement of DSSC performances. Thus, in the present study, TiO2/N3, ZnO/N3, ZnO-TiO2/N3, TiO2/N3/Ag, ZnO/N3/Ag, and ZnO-TiO2/N3/Ag assemblies have been fabricated and their CT processes have been monitored by using surface-enhanced Raman scattering (SERS) spectra, with particular focus on the differences caused by the synergistic effect of the ZnO-TiO2 component. The dye loading capacity of the dendritic crystal ZnO-TiO2 is much larger than that of TiO2. There are extra enhancements in the SERS intensity and degree of CT (ρCT) in ZnO-TiO2/N3 compared to ZnO + TiO2/N3 (based on a simulation curve for the physically mixed TiO2 and ZnO semiconductors) with 476.5 nm excitation due to the synergistic effect of the ZnO-TiO2 component. And these enhancements in ZnO-TiO2/N3/Ag compared to ZnO + TiO2/N3/Ag appear with 476.5 and 532 nm excitation, which are particularly large with 532 nm excitation. Accordingly, the participation of Ag in this synergistic effect can reduce its energy threshold, which will make it easier to appear. Finally, to rationalize these extra enhancements, the models describing the CT mechanism have been proposed. Thus, the use of the dendritic crystal ZnO-TiO2 composite semiconductor in the semiconductor/N3/Ag system can improve the adsorption capacity of N3 compared to that with TiO2. Meanwhile, the synergistic effect of ZnO-TiO2 and Ag can promote the CT process, demonstrating that ZnO-TiO2/N3/Ag is an excellent structure for DSSCs.

[1]  C. Park,et al.  Synthesis, characterization, and photocatalytic properties of ZnO nano-flower containing TiO2 NPs , 2012 .

[2]  Z. Li,et al.  One-dimensional CdS/TiO2 nanofiber composites as efficient visible-light-driven photocatalysts for selective organic transformation: synthesis, characterization, and performance. , 2015, Langmuir : the ACS journal of surfaces and colloids.

[3]  S. Skrabalak,et al.  Achieving Synergy with a Potential Photocatalytic Z-Scheme: Synthesis and Evaluation of Nitrogen-Doped TiO2/SnO2 Composites , 2012 .

[4]  Hea-Yeon Lee,et al.  Aggregation effect of silver nanoparticles on the energy conversion efficiency of the surface plasmon-enhanced dye-sensitized solar cells , 2014 .

[5]  Zhilin Yang,et al.  Dimeric Core–Shell Ag2@TiO2 Nanoparticles for Off-Resonance Raman Study of the TiO2–N719 Interface , 2015 .

[6]  Chun‐Hu Chen,et al.  Graphene thickness-controlled photocatalysis and surface enhanced Raman scattering. , 2014, Nanoscale.

[7]  M. Dissanayake,et al.  Efficiency enhancement in plasmonic dye-sensitized solar cells with TiO2 photoanodes incorporating gold and silver nanoparticles , 2015, Journal of Applied Electrochemistry.

[8]  De‐Yin Wu,et al.  Raman spectroscopic investigation on TiO2-N719 dye interfaces using Ag@TiO2 nanoparticles and potential correlation strategies. , 2013, Chemphyschem : a European journal of chemical physics and physical chemistry.

[9]  Q. Cong,et al.  Charge-Transfer Effect on Surface-Enhanced Raman Scattering (SERS) in an Ordered Ag NPs/4-Mercaptobenzoic Acid/TiO2 System , 2015 .

[10]  Fang‐Xing Xiao.  Construction of highly ordered ZnO-TiO2 nanotube arrays (ZnO/TNTs) heterostructure for photocatalytic application. , 2012, ACS applied materials & interfaces.

[11]  Zhilin Yang,et al.  Adsorption of Dye Molecules on Single Crystalline Semiconductor Surfaces: An Electrochemical Shell-Isolated Nanoparticle Enhanced Raman Spectroscopy Study , 2016 .

[12]  John R. Lombardi,et al.  A Unified Approach to Surface-Enhanced Raman Spectroscopy , 2008 .

[13]  Y. Ozaki,et al.  Generation of Pronounced Resonance Profile of Charge-Transfer Contributions to Surface-Enhanced Raman Scattering , 2012 .

[14]  E. Yu,et al.  Enhanced semiconductor optical absorption via surface plasmon excitation in metal nanoparticles , 2005 .

[15]  O. Diwald,et al.  Particle Networks from Powder Mixtures: Generation of TiO2–SnO2 Heterojunctions via Surface Charge-Induced Heteroaggregation , 2012, The journal of physical chemistry. C, Nanomaterials and interfaces.

[16]  D. Meisel,et al.  Adsorption and surface-enhanced Raman of dyes on silver and gold sols , 1982 .

[17]  Qiang Zhang,et al.  Effects of calcination on the photocatalytic properties of nanosized TiO2 powders prepared by TiCl4 hydrolysis , 2000 .

[18]  Chun‐Sing Lee,et al.  Synthesis of In2O3-In2S3 core-shell nanorods with inverted type-I structure for photocatalytic H2 generation. , 2013, Physical chemistry chemical physics : PCCP.

[19]  B. Liao,et al.  Preparation of nanosized TiO2/ZnO composite catalyst and its photocatalytic activity for degradation of methyl orange , 2008 .

[20]  Anders Hagfeldt,et al.  Light-Induced Redox Reactions in Nanocrystalline Systems , 1995 .

[21]  R. R. Philip,et al.  Electrochemical Synthesis of Novel Zn-Doped TiO2 Nanotube/ZnO Nanoflake Heterostructure with Enhanced DSSC Efficiency , 2016, Nano-micro letters.

[22]  Bing Zhao,et al.  Investigation of Charge Transfer in Ag/N719/TiO2 Interface by Surface-Enhanced Raman Spectroscopy , 2016 .

[23]  Koichi Yamada,et al.  Effects of silver particles on the photovoltaic properties of dye-sensitized TiO2 thin films , 2000 .

[24]  Hanqing Yu,et al.  Degradation of refractory pollutants under solar light irradiation by a robust and self-protected ZnO/CdS/TiO2 hybrid photocatalyst. , 2016, Water research.

[25]  Nam-Gyu Park,et al.  High efficiency solid-state sensitized solar cell-based on submicrometer rutile TiO2 nanorod and CH3NH3PbI3 perovskite sensitizer. , 2013, Nano letters.

[26]  Hongyuan Wei,et al.  Measurement of wurtzite ZnO/rutile TiO2 heterojunction band offsets by x-ray photoelectron spectroscopy , 2011 .

[27]  Chunxu Wang,et al.  Scanned chemical enhancement of surface-enhanced Raman scattering using a charge-transfer complex. , 2011, Chemical communications.

[28]  Yanbiao Liu,et al.  Enhanced Photoelectrochemical Properties of Cu2O-loaded Short TiO2 Nanotube Array Electrode Prepared by Sonoelectrochemical Deposition , 2010 .

[29]  S. Zakeeruddin,et al.  Molecular engineering of push-pull porphyrin dyes for highly efficient dye-sensitized solar cells: the role of benzene spacers. , 2014, Angewandte Chemie.

[30]  Hao Gong,et al.  Hierarchical assembly of ZnO nanostructures on SnO(2) backbone nanowires: low-temperature hydrothermal preparation and optical properties. , 2009, ACS nano.

[31]  Hongzhi Wang,et al.  Capillary microchannel-based microreactors with highly durable ZnO/TiO2 nanorod arrays for rapid, high efficiency and continuous-flow photocatalysis , 2010 .

[32]  Jihuai Wu,et al.  Electrolytes in dye-sensitized solar cells. , 2015, Chemical reviews.

[33]  Basile F. E. Curchod,et al.  Dye-sensitized solar cells with 13% efficiency achieved through the molecular engineering of porphyrin sensitizers. , 2014, Nature chemistry.

[34]  A. Belcher,et al.  Highly efficient plasmon-enhanced dye-sensitized solar cells through metal@oxide core-shell nanostructure. , 2011, ACS nano.

[35]  Jianfeng Chen,et al.  Visible-light-responsive TiO2-coated ZnO:I nanorod array films with enhanced photoelectrochemical and photocatalytic performance. , 2015, ACS applied materials & interfaces.

[36]  M. Grätzel,et al.  A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films , 1991, Nature.

[37]  Chunxiang Xu,et al.  3D Ag/ZnO hybrids for sensitive surface-enhanced Raman scattering detection , 2016 .

[38]  Yukihiro Ozaki,et al.  Semiconductor-enhanced Raman scattering: active nanomaterials and applications. , 2017, Nanoscale.

[39]  Y. Ozaki,et al.  Fabrication of a highly sensitive surface-enhanced Raman scattering substrate for monitoring the catalytic degradation of organic pollutants , 2015 .

[40]  M. S. Kamal,et al.  Synthesis of zinc oxide/titanium dioxide (ZnO/TiO2) nanocomposites by wet incipient wetness impregnation method and preparation of ZnO/TiO2 paste using poly(vinylpyrrolidone) for efficient dye-sensitized solar cells , 2016 .

[41]  Federico Bella,et al.  Aqueous dye-sensitized solar cells. , 2015, Chemical Society reviews.

[42]  Mohammad Khaja Nazeeruddin,et al.  Perovskite as light harvester: a game changer in photovoltaics. , 2014, Angewandte Chemie.

[43]  Y. Ozaki,et al.  Charge Transfer at the TiO2/N3/Ag Interface Monitored by Surface-Enhanced Raman Spectroscopy , 2017 .

[44]  Yanlin Song,et al.  The Ag shell thickness effect of Au@Ag@SiO2 core-shell nanoparticles on the optoelectronic performance of dye sensitized solar cells. , 2016, Chemical communications.

[45]  Yu Hou,et al.  Fabrication of regular ZnO/TiO2 heterojunctions with enhanced photocatalytic properties. , 2013, Chemistry.

[46]  R. Birke,et al.  A unified view of surface-enhanced Raman scattering. , 2009, Accounts of chemical research.

[47]  G. Cao,et al.  Efficiency Enhancement of Quantum Dot Sensitized TiO2/ZnO Nanorod Arrays Solar Cells by Plasmonic Ag Nanoparticles. , 2016, ACS applied materials & interfaces.

[48]  Kuang-Che Lee,et al.  Size effect of Ag nanoparticles on surface plasmon resonance , 2008 .

[49]  Da Chen,et al.  Preparation and Enhanced Photoelectrochemical Performance of Coupled Bicomponent ZnO−TiO2 Nanocomposites , 2008 .

[50]  Hui‐Ming Cheng,et al.  CdS–mesoporous ZnS core–shell particles for efficient and stable photocatalytic hydrogen evolution under visible light , 2014 .

[51]  Guo-Qiang Lo,et al.  Improved dye-sensitized solar cells with a ZnO-nanoflower photoanode , 2007 .