A composite film of nickel sulfide/platinum/titanium foil (NiS/Pt/Ti) with low cost and high electrocatalytic activity was synthesized by the use of an in situ electropolymerization route and proposed as a counter electrode (CE) catalyst for flexible dye-sensitized solar cells (FDSSCs). The FDSSC with the NiS/Pt/Ti CE exhibited a comparable power conversion efficiency of 7.20% to the FDSSC with the platinum/titanium (Pt/Ti) CE showing 6.07%. The surface morphology of the NiS/Pt/Ti CE with one-dimensional (1D) structure is characterized by using the scanning electron microscopy (SEM). The NiS/Pt/Ti CE also displayed multiple electrochemical functions of excellent conductivity, great electrocatalytic ability for iodine/triiodine, and low charge transfer resistance of 2.61 ± 0.02 Ω cm2, which were characterized by using the cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and Tafel polarization plots. The photocurrent-photovoltage (J-V) character curves were further used to calculate the theoretical optical light performance parameters of the FDSSCs. It may be said that the NiS/Pt/Ti counter electrode is a promising catalytic material to replace the expensive platinum in FDSSCs.

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A highly efficient flexible dye-sensitized solar cell based on nickel sulfide/platinum/titanium counter electrode

Electrolytes in Dye-Sensitized Solar Cells

The pressure to move towards renewable energy has inspired researchers to look for ideas in photovoltaics that may lead to a major breakthrough. Recently the use of perovskites as a light harvester has lead to stunning progress. The power conversion efficiency of perovskite solar cells is now approaching parity (>22 %) with that of the established technology which took decades to reach this level of performance. The use of a hole transport material (HTM) remains indispensable in perovskite solar cells. Perovskites can conduct holes, but they are present at low levels, and for efficient charge extraction a HTM layer is a prerequisite. Herein we provide an overview of the diverse types of HTM available, from organic to inorganic, in the hope of encouraging further research and the optimization of these materials.

Hole‐Transport Materials for Perovskite Solar Cells

http://nanofm.mse.gatech.edu/Papers/20150404MaterialsToday.pdf

Recent advances in dye-sensitized solar cells: from photoanodes, sensitizers and electrolytes to counter electrodes

Single crystals of hybrid perovskites have shown remarkably improved physical properties compared to their polycrystalline film counterparts, underscoring their importance in the further development of advanced semiconductor devices. Here we present a new method of growing sizable CH3NH3PbCl3 single crystals based on the retrograde solubility behavior of hybrid perovskites. We show, for the first time, the energy band structure, charge recombination, and transport properties of CH3NH3PbCl3 single crystals. These crystals exhibit trap-state density, charge carrier concentration, mobility, and diffusion length comparable with the best quality crystals of methylammonium lead iodide or bromide perovskites reported so far. The high quality of the crystal along with its suitable optical band gap enabled us to build an efficient visible-blind UV-photodetector, demonstrating its potential in optoelectronic applications.

CH3NH3PbCl3 Single Crystals: Inverse Temperature Crystallization and Visible-Blind UV-Photodetector.

NiS2 nanoparticles and nanocomposites of NiS2 with reduced graphene oxide (NiS2@RGO) have been successfully prepared via a facile hydrothermal reaction of nickel ions and sulfur source in the absence or presence of graphene oxide. NiS2@RGO nanocomposites exhibit excellent electrocatalytic performance for reduction of triiodide, owing to the improved conductivity and positive synergetic effect between NiS2 and RGO. As a consequence, the dye-sensitized solar cell with the NiS2@RGO counter electrode (CE) produces a power conversion efficiency of 8.55%, which is higher than that (7.02%) for the DSSC with the NiS2 CE, higher than that (3.14%) for the DSSC with the RGO CE, and also higher than that (8.15%) for the DSSC with the reference Pt CE under the same conditions.

NiS2/Reduced Graphene Oxide Nanocomposites for Efficient Dye-Sensitized Solar Cells

A TiO2-nanotube-array-based photocatalytic fuel cell using refractory organic compounds as substrates for electricity generation.

ConspectusSolar energy is the most abundant renewable energy available to the earth and can meet the energy needs of humankind, but efficient conversion of solar energy to electricity is an urgent issue of scientific research. As the third-generation photovoltaic technology, dye-sensitized solar cells (DSSCs) have gained great attention since the landmark efficiency of ∼7% reported by O’Regan and Gratzel. The most attractive features of DSSCs include low cost, simple manufacturing processes, medium-purity materials, and theoretically high power conversion efficiencies. As one of the key materials in DSSCs, the counter electrode (CE) plays a crucial role in completing the electric circuit by catalyzing the reduction of the oxidized state to the reduced state for a redox couple (e.g., I3–/I–) in the electrolyte at the CE–electrolyte interface. To lower the cost caused by the typically used Pt CE, which restricts the large-scale application because of its low reserves and high price, great effort has been ma...

Metal Selenides as Efficient Counter Electrodes for Dye-Sensitized Solar Cells

A series of symmetrical donor–acceptor–donor (D–A–D) chromophores bearing various electron-withdrawing groups, such as quinoxaline (Qx), benzo[g]quinoxaline (BQ), phenazine (Pz), benzo[b]phenazine (BP), thieno[3,4-b]pyrazine (TP), and thieno[3,4-b]quinoxaline (TQ), has been designed and synthesized. Intramolecular charge transfer (ICT) interactions can be found for all the chromophores due to the electron-withdrawing properties of the two imine nitrogens in the pyrazine ring and the electron-donating properties of the other two amine nitrogens in the two triphenylamines. Upon the fusion of either benzene or thiophene ring on the pyrazine acceptor unit, the ICT interactions are strengthened, which results in the bathochromically shifted ICT band. Moreover, the thiophene ring is superior to the benzene ring in enlarging the ICT interaction and expanding the absorption spectrum. Typically, when a thiophene ring is fused on the Qx unit in DQxD, a near-infrared dye is realized in simple chromophore DTQD, which...

Controlling the Charge Transfer in D–A–D Chromophores Based on Pyrazine Derivatives

Perovskite solar cells are very promising for practical applications owing to their rapidly rising power conversion efficiency and low cost of solution-based processing. 2,2′,7,7′-Tetrakis(N,N-di-p-methoxyphenylamine) 9,9′-spirobifluorene (Spiro-OMeTAD) is most widely used as a hole-transporting material (HTM) in perovskite solar cells. However, the tedious synthesis and high cost of Spiro-OMeTAD inhibit its commercial-scale application in the photovoltaic industry. In this article, we report a carbazole-based compound (R01) as a new HTM in efficient perovskite solar cells. R01 is synthesized via a facile route consisting of only two steps from inexpensive commercially available materials. Furthermore, R01 exhibits higher hole mobility and conductivity than the state-of-the-art Spiro-OMeTAD. Perovskite solar cells fabricated with R01 produce a power conversion efficiency of 12.03%, comparable to that obtained in devices using Spiro-OMeTAD in this study. Our findings underscore R01 as a highly promising HT...

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Zhong-Sheng Wang

Papers

NiS2/Reduced Graphene Oxide Nanocomposites for Efficient Dye-Sensitized Solar Cells

A TiO2-nanotube-array-based photocatalytic fuel cell using refractory organic compounds as substrates for electricity generation.

Metal Selenides as Efficient Counter Electrodes for Dye-Sensitized Solar Cells

Controlling the Charge Transfer in D–A–D Chromophores Based on Pyrazine Derivatives

Facile Synthesis and High Performance of a New Carbazole-Based Hole-Transporting Material for Hybrid Perovskite Solar Cells