Shuqing Huang

Dye-sensitized solar cells with NiS counter electrodes electrodeposited by a potential reversal technique

Nickel sulfides have been, for the first time, electrodeposited on transparent conductive glass by a facile periodic potential reversal (PR) technique to supersede Pt counter electrodes (CEs) of dye-sensitized solar cells (DSCs). The composition and electrochemical catalytic activity of the nickel sulfide films prepared by PR technique are different from those of the ones deposited by the commonly used potentiostatic (PS) technique. PR technique produces transparent single-component NiS, while co-deposition of Ni and NiS is found in the opaque films prepared by PS method. The nickel sulfide deposited by PR technique shows high catalytic activity for the reduction of I3− to I− in a DSC. DSC with the CE deposited by PR technique performs much better (6.82%) than that by PS method (3.22%), and is comparable to the device with conventional Pt coated CE (7.00%).

Fibrous CdS/CdSe quantum dot co-sensitized solar cells based on ordered TiO2 nanotube arrays

A new kind of fibrous quantum dot sensitized solar cell has been designed and fabricated by using CdS and CdSe co-sensitized TiO(2) nanotubes on Ti wire as the photoanode and highly active Cu(2)S as the counter electrode. By optimizing the CdSe deposition time and the length of the nanotube, a power conversion efficiency of 3.18% has been obtained under AM 1.5 illumination (100 mW cm(-2)). The potential application of this kind of solar cell has also been discussed in this paper.

Low-Cost Flexible Nano-Sulfide/Carbon Composite Counter Electrode for Quantum-Dot-Sensitized Solar Cell

Cu2S nanocrystal particles were in situ deposited on graphite paper to prepare nano-sulfide/carbon composite counter electrode for CdS/CdSe quantum-dot-sensitized solar cell (QDSC). By optimization of deposition time, photovoltaic conversion efficiency up to 3.08% was obtained. In the meantime, this composite counter electrode was superior to the commonly used Pt, Au and carbon counter electrodes. Electrochemical impedance spectra further confirmed that low charge transfer resistance at counter electrode/electrolyte interface was responsible for this, implied the potential application of this composite counter electrode in high-efficiency QDSC.

Carbon nanotube counter electrode for high-efficient fibrous dye-sensitized solar cells

High-efficient fibrous dye-sensitized solar cell with carbon nanotube (CNT) thin films as counter electrodes has been reported. The CNT films were fabricated by coating CNT paste or spraying CNT suspension solution on Ti wires. A fluorine tin oxide-coated CNT underlayer was used to improve the adherence of the CNT layer on Ti substrate for sprayed samples. The charge transfer catalytic behavior of fibrous CNT/Ti counter electrodes to the iodide/triiodide redox pair was carefully studied by electrochemical impedance and current-voltage measurement. The catalytic activity can be enhanced by increasing the amount of CNT loading on substrate. Both the efficiencies of fibrous dye-sensitized solar cells using paste coated and sprayed CNT films as counter electrodes are comparative to that using Pt wires, indicating the feasibility of CNT/Ti wires as fibrous counter electrode for superseding Pt wires.

Front-side illuminated CdS/CdSe quantum dots co-sensitized solar cells based on TiO2 nanotube arrays

We fabricated a front-side illuminated CdS/CdSe quantum dots co-sensitized solar cell based on TiO(2) nanotube arrays. The freestanding TiO(2) nanotube arrays were first detached from anodic oxidized Ti foils and then transferred to the fluorine-doped tin oxide to form photoanodes. An opaque Cu(2)S with high electrochemical activity was used as the counter electrode. A photovoltaic conversion efficiency as high as 3.01% under one sun illumination has been achieved after optimizing the deposition time of CdSe quantum dots and the length of the TiO(2) nanotube arrays. It is observed that the power conversion efficiency of quantum dots sensitized solar cells from the front-side illumination mode (3.01%) is much higher than that of the back-side illumination mode (1.32%) owing to the poor catalytic activity of Pt to polysulfide electrolytes and light absorption by the electrolytes for the latter.

Highly efficient fibrous dye-sensitized solar cells based on TiO2 nanotube arrays

The structure of fibrous dye-sensitized solar cells, which were constructed by a TiO(2) nanotube array on Ti wire as the photoanode twisted by a Pt wire counter electrode, has been first systematically investigated by accurately controlling the thread pitch distance of screwed Pt wire. It has been revealed that the thread pitch will strongly influence the photovoltaic performance and kinetic processes in fibrous solar cells. The effect of the length of the TiO(2) nanotube on cell performance has also been discussed. After optimization, a relatively universal optimized thread pitch value of 1 mm for fibrous DSCs has been proved and the light-to-electricity conversion efficiency has been remarkably improved to 5.84%.

The potential of eutectic mixtures as environmentally friendly, solvent-free electrolytes for dye-sensitized solar cells

A new kind of solvent-free eutectic melt electrolytes for dye-sensitized solar cells (DSCs) has been designed, which are composed of imidazolium salts (i.e. 1-methyl-3-acetylimidazolium iodide (MAII), 1-ethyl-3-methylimidazolium iodide (EMII)) and plastic crystal succinonitrile (SN). Differential scanning calorimetric measurement reveals that the eutectic melt mixture EMII/SN can exhibit stable liquid state in the whole temperature domain from −80 to 80 °C. Besides, the conductivities of the eutectic melt electrolytes are higher than conventional imidazolium-based ionic liquid, 1-propyl-3-methylimidazolium iodide (PMII). Up to 7.46% of light-to-electricity conversion efficiency has been achieved by using the SN-based eutectic melt electrolyte, higher than PMII-based DSCs. Besides, the devices based on eutectic melt electrolytes exhibit good thermal stability. These results show that succinonitrile-based eutectic melts as environmentally friendly electrolytes, possess great potential for large-scale outdoor application of DSCs.

REFLECTANCE AND LUMINESCENCE SPECTRA OF CAS-PR PHOSPHORS

Abstract Reflectance spectra and photoluminescence from the ultraviolet (UV) to the near infrared (NIR) have been studied for CaS:Pr phosphors of different concentrations. The absolute intensities of eight bands between UV and NIR have been measured. These bands result from forced electric-dipole transitions between the 3H4 ground manifold and various excited J manifolds of the Pr3+ ion. The transition intensities have been accounted for in terms of three phenomenological parameters with an rms error of 6–10%. By applying the Judd-Ofelt theory and by using the photoluminescence spectral patterns, the spontaneous emission probabilities and relaxation rates of fluorescent states have been determined. The measured fluorescence lifetimes of the 1 D 2 → 3 H 5 transition of CaS:Pr (0.5 and 1.0 M%) are in good agreement with the theoretical values. The emission cross sections for the fluorescent states of 3 P 1 → 3 F 3 , 3 P 0 → 3 F 2 have been measured by using the Judd-Ofelt technique.