Bencai Lin

Improvement of the humidity stability of organic–inorganic perovskite solar cells using ultrathin Al2O3 layers prepared by atomic layer deposition

For the successful commercialization of organic–inorganic halide perovskite solar cells, it is necessary to ensure their stability in addition to high efficiency. In this study, the degradation mechanism of organic–inorganic halide structures in humidity was investigated computationally. Owing to the high polarity of water molecules, the unprotected organic–inorganic structure will inevitably decompose in a humid environment. To improve the ambient stability of the organic–inorganic perovskite solar cells, we introduced an interface modification method using ultrathin compact aluminum oxide (Al2O3) layers deposited by atomic layer deposition (ALD). The experimental results showed the ambient stability of the organic–inorganic perovskite solar cell with an ultrathin compact Al2O3 layer was greatly improved without a significant reduction in efficiency.

Alkaline imidazolium- and quaternary ammonium-functionalized anion exchange membranes for alkaline fuel cell applications

Alkaline imidazolium-type ionic liquids (ILs) and quaternary ammonium salt functionalized alkaline anion-exchange membranes (AEMs), with the same ion exchange capacity (IEC), were synthesized via in situ cross-linking of styrene, acrylonitrile, 1-methyl-3-(4-vinylbenzyl)imidazolium chloride ([MVBIm][Cl]), and N,N,N-trimethyl-1-(4-vinylphenyl) methanaminium chloride ([TMVPMA][Cl]), respectively. The water uptake, swelling ratio, conductivity, and alkaline stability of resultant cross-linked copolymer membranes were investigated. Both types of copolymer membranes exhibit hydroxide conductivity above 10−2 S cm−1 at room temperature. Alkaline imidazolium-type IL functionalized membranes showed an excellent chemical stability of up to 1000 h without obvious loss of ion conductivity, whereas the membranes based on quaternary ammonium salts degraded in high pH solution because of nucleophillic substitution on quaternary ammonium cations. The results of this study suggest that the AEMs based on alkaline imidazolium-type ILs are expected to promote the widespread use of alkaline fuel cells.

High-Temperature Solid-State Dye-Sensitized Solar Cells Based on Organic Ionic Plastic Crystal Electrolytes

Organic ionic plastic crystal, 1-ethyl-1-methyl pyrrolidinium iodide (P(12) I), is employed as the solid-state electrolytes for dye-sensitized solar cells. The fabricated solid-state devices show an overall power conversion efficiency of ~5.8% under AM 1.5 radiation (50 mW/cm(2) ) and excellent long-term stability at 80 °C.

A promising alternative solvent of perovskite to induce rapid crystallization for high-efficiency photovoltaic devices

As solar cell structures based on planar heterojunctions have already demonstrated very impressive advances in cost-effectiveness and performance, many different solvents are being developed and gradually adopted for high-performance inorganic–organic hybrid perovskite solar cells. Here, we introduce a simple planar cell configuration with layers prepared in a fully solution-based process, in which dimethylacetamide (DMAC) serves as an effective precursor solvent that is comparable with N,N-dimethylformamide (DMF). The use of DMAC leads to a smooth and dense perovskite film via one-step deposition, whose ideal morphology enables solar cells to obtain a high power-conversion efficiency of 15.12%. We also studied the effect of different solvents through a computation of the stabilization energy between PbI2, CH3NH3I, and solvent molecules. These results offer insight into the promising directions for the development of solvent engineering.

Polybenzimidazole/zwitterion-coated silica nanoparticle hybrid proton conducting membranes for anhydrous proton exchange membrane application

Polybenzimidazole (PBI)/H3PO4/zwitterion-coated silica nanoparticle hybrid proton conducting membranes for anhydrous proton-exchange membrane application were synthesized and characterized. Fluorine-containing PBI was synthesized via the condensation polymerization of 3,3-diaminobenzidine and 2-bis(4-carboxyphenyl) hexafluoropropane in poly(phosphoric acid) at 170 °C. Zwitterion-coated silica nanoparticles were synthesized via the hydrolysis and polycondensation of zwitterionic organosiloxane, and applied as the additive for the PBI-based hybrid proton conducting membranes. The synthesized phosphoric acid doped polymeric composite membranes were transparent, flexible and showed high proton conductivities of up to 1 × 10−2 S cm−1 at 160 °C under anhydrous conditions. Addition of zwitterion-coated silica nanoparticles to the PBI membrane dramatically increased the phosphoric acid doping capacity, and slightly improved the chemical stability of the composite membranes. Compared with pure PBI membranes, zwitterion-coated SiO2 nanoparticles are effective in preventing the release of the phosphoric acid component from the composite membranes. These properties enable this type of hybrid membrane to be suitable for high-temperature polymer electrolyte membrane fuel cells.

Poly(ionic liquid)/ionic liquid/graphene oxide composite quasi solid-state electrolytes for dye sensitized solar cells

Poly(ionic liquid)/ionic liquid/graphene oxide (poly(IL)/IL/GO) composite gel electrolytes containing poly(1-butyl-3-vinylimidazolium bis(trifluoromethanesulfonyl)imide), 1-propyl-3-methylimidazolium iodide and graphene oxide are prepared for dye-sensitized solar cells (DSSCs), without any volatile organic solvent. The conductivity of the composite electrolyte is significantly increased by adding an appropriate amount of GO, and the DSSCs based on composite electrolytes containing GO show higher power conversion efficiency performance and better long-term stability compared to those without GO. The DSSC based on the composite electrolytes which contain 2 wt% of GO show an overall power conversion efficiency of 4.83% under simulated AM 1.5 solar spectrum irradiation. The superior long-term stability of the DSSCs indicates that this type of composite electrolyte could overcome the drawbacks of volatile liquid electrolytes, and offer a feasible method to fabricate DSSCs in future practical applications.

Improved photovoltaic performance in perovskite solar cells based on CH3NH3PbI3 films fabricated under controlled relative humidity

Because organic–inorganic perovskite solar cells are known to be unstable in the presence of moisture, most of the reported high-efficiency perovskite solar cells are fabricated under an inert atmosphere in a glove box. This requirement impedes mass production of organic–inorganic perovskite solar cells (PVSCs). Fabricating dense uniform perovskite thin films with high surface coverage via a single one-step solution process is also a challenge in achieving high-efficiency PVSCs. In this work, we successfully develop a facile, controllable one-step solution processing method to obtain high-quality hybrid-perovskite thin films in ambient atmosphere. The entire preparation process for CH3NH3PbI3 films is conducted in ambient air to investigate the effect of humidity on the molecular structure and crystallization of the hybrid perovskite. It is found that relative humidity (RH) and solvent are crucial factors in determining the final morphology of CH3NH3PbI3 and the photovoltaic performance. The best device efficiency achieved for a solar cell fabricated in ambient atmosphere under a RH of 28% is 16.15%; this PCE value is comparable to that of glove box-based PVSCs. This work puts forth a possible method for the easy mass production of high-performance PVSCs under ambient conditions.

Performance enhancement of perovskite solar cells with a modified TiO2 electron transport layer using Zn-based additives

Perovskite solar cells (PVSCs) have recently emerged as a very attractive option in film photovoltaics. Both solvent-engineering techniques and electron transport layer (ETL) properties are necessary for high-performance PVSCs. Herein, we report a one-step spin-coating approach for the preparation of uniform and dense perovskite layers, using a mixed solvent of dimethylacetamide (DMAC) and N-methyl-2-pyrrolidone (NMP) followed by exposure to toluene to induce crystallization. We also developed a simple and quantitative method to improve the traditional compact TiO2 ETL properties and device performance based on Zn precursor doping. The effect of Zn-doped TiO2 was investigated using atomic force microscopy, ultraviolet-visible spectra, photoluminescence, and open-circuit photovoltage decays. The results indicate that Zn-doped TiO2 provides a better interface between the ETL and perovskite layer than non-doped TiO2. Light Zn doping (2 vol%) was found to be the most effective additive, and the average power conversion efficiency improved from 13.61% to 15.25%.

Solvothermal preparation of phthalocyanine nanorod/rGO composites and their application to visible-light-responsive photocatalysts

Phthalocyanine (Pc) nanorod/reduced graphene oxide (rGO) composites were prepared by a simple solvothermal method, in which Pc nanosheet and graphene oxide (GO) suspensions were mixed in methanol. As characterized by scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction, Pc nanorods with an amorphous structure and an average diameter of 250nm are partially covered by rGO sheets. In the photodegradation experiments, all the composites with different rGO content show enhanced photocatalytic activity for Rhodamine B decomposition under visible-light compared to pure Pc nanorods or rGO sheets. The enhanced photocatalytic activity shall be ascribed to the large surface area offered by rGO and the charge-transfer from Pc to rGO as indicated by the photoluminescence measurement, in which fluorescence intensity of the composites is much weaker than that of Pc nanorods.

Nitrogen-doped three-dimensional graphene-supported platinum catalysts for polymer electrolyte membrane fuel cells application

Catalysts are a key component of polymer electrolyte membrane fuel cells (PEMFCs). In this work, nitrogen-doped three-dimensional graphene-supported platinum (Pt-3DNG) catalysts are successfully prepared and characterized. SEM and TEM images show the Pt nanoparticles are uniformly dispersed in the sheets of nitrogen-doped 3DNG. Compared with that of the commercial Pt/C catalysts, Pt-3DNG show much better oxygen reduction reaction (ORR) activity and cycling stability, and the reduction in limit current density after 1000 cycles is only about 1.6% for the Pt-3DNG catalysts, whereas 7.2% for the commercial Pt/C catalysts. The single cell using Pt-3DNG catalysts in both the anode and the cathode show a higher peak power density (21.47mW cm−2) than that using commercial Pt/C catalysts (20.17mW cm−2) under the same conditions. These properties make this type of catalyst suitable for the application in PEMFCs.