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Zhu W.,Nanjing University | Kang L.,Nanjing University | Yu T.,Nanjing University | Yu T.,Jiangsu Key Laboratory for Nano Technology | And 7 more authors.
ACS Applied Materials and Interfaces | Year: 2017

Herein, we demonstrate that the facile face-down annealing route which effectively confines the evaporation of residual solvent molecules in one-step deposited precursor films can controllably enable the formation of (110) textured CH3NH3PbI3 films consisting of high-crystallinity well-ordered micrometer-sized grains that span vertically the entire film thickness. Such microstructural features dramatically decrease nonradiative recombination sites as well as greatly improve the transport property of charge carries in the films compared with that of the nontextured ones obtained by the conventional annealing route. As a consequence, the planar-heterojunction perovskite solar cells with these textured CH3NH3PbI3 films exhibit significantly enhanced power conversion efficiency (PCE) along with small hysteresis and excellent stability. The champion cell yields impressive PCE boosting to 18.64% and a stabilized value of around 17.22%. Particularly, it can maintain 86% of its initial value after storage for 20 days in ambient conditions with relative humidity of 10-20%. Our work suggests a facile and effective route for further boosting the efficiency and stability of low-cost perovskite solar cells. © 2017 American Chemical Society.


Wu B.,Nanjing University | Zhao M.,Nanjing University | Shi W.,Dalian Sunrise Power Co. | Liu W.,Nanjing University | And 8 more authors.
International Journal of Hydrogen Energy | Year: 2014

Accelerated stress tests (ASTs) were performed to study the degradation mechanism of Nafion/PTFE composite membrane in PEM fuel cell with intensive RH cycling and load cycling. It was recognized that the edge of membrane electrode assembly (MEA) should be carefully treated to prevent the immediate failure for excessive or non-uniform mechanical stress mainly caused by RH cycling in the early period of ASTs. A long accelerated life (over 1000 h) was obtained for MEA with an edge protection and a hot-pressing process along with a low hydrogen permeation current. In addition, the decay of open circuit voltage, the fluoride emission rate (FER) from cathode side and the polarization curves were also monitored during the test. It was verified that the chemical degradation of membrane occurred inevitably caused by radical attack (HO, HO2 and H2O2) due to the intensification of gas mutual permeation. Membrane thinning, Pt particles gathering along the interfaces, even ionomer disappearing at cathode side could be observed from TEM and SEM results. Besides, open circuit voltage under H2/N2 atmosphere of MEA was confirmed to be a rapid diagnose tool of membrane physical condition. © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.


Li F.,National Renewable Energy Laboratory | Zhu W.,National Renewable Energy Laboratory | Bao C.,National Renewable Energy Laboratory | Yu T.,National Renewable Energy Laboratory | And 7 more authors.
Chemical Communications | Year: 2016

Laser irradiation as a rapid crystallization approach was successfully introduced to prepare homogeneous, dense-grained CH3NH3PbI3 films. Planar-heterojunction solar cells employing these high-quality films showed the optimal efficiency of 17.8% with a remarkably high open-circuit voltage of 1.146 V. © The Royal Society of Chemistry 2016.


Zhu W.,Nanjing University | Yu T.,Nanjing University | Yu T.,Jiangsu Key Laboratory for Nano Technology | Li F.,Nanjing University | And 8 more authors.
Nanoscale | Year: 2015

A high-quality CH3NH3PbI3 film is crucial in the manufacture of a high-performance perovskite solar cell. Here, a recrystallization process via facile fumigation with DMF vapor has been successfully introduced to self-repair of CH3NH3PbI3 films with poor coverage and low crystallinity prepared by the commonly used one-step spin-coating method. We found that the CH3NH3PbI3 films with dendritic structures can spontaneously transform to the uniform ones with full coverage and high crystallinity by adjusting the cycles of the recrystallization process. The mesostructured perovskite solar cells based on these repaired CH3NH3PbI3 films showed reproducible optimal power conversion efficiency (PCE) of 11.15% and average PCE of 10.25 ± 0.90%, which are much better than that of devices based on the non-repaired CH3NH3PbI3 films. In addition, the hysteresis phenomenon in the current-voltage test can also be effectively alleviated due to the quality of the films being improved in the optimized devices. Our work proved that the fumigation of solvent vapor can modify metal organic perovskite films such as CH3NH3PbI3. It offers a novel and attractive way to fabricate high-performance perovskite solar cells. This journal is © The Royal Society of Chemistry 2015.


Zhu W.,Nanjing University | Bao C.,Nanjing University | Lv B.,Nanjing University | Li F.,Nanjing University | And 8 more authors.
Journal of Materials Chemistry A | Year: 2016

A homogeneous cap-mediated crystallization concept with face-to-face configuration is proposed here to modulate the crystallization kinetics of organolead triiodide perovskite (OTP) films in a controlled way. The introduced OTP caps, especially those with low surface roughness, play a dramatically positive role in retarding the nucleation rate, promoting the growth, and preventing the composition loss of OTP grains, fully facilitating the formation of pinhole-free OTP films with numerous desirable characteristics, such as greatly enlarged grains, vertically aligned grain boundaries, preferred (110) orientation, significantly improved crystallinity, and proper stoichiometry. As a consequence, planar-heterojunction solar cells incorporating these high-quality films deliver a promising average efficiency of 17.87%, showing a remarkable enhancement of approximately 30% compared with control samples. In particular, large fill factors can be routinely achieved in these high efficiency cells. This excellent performance mainly originates from greatly suppressed non-radiative recombination as well as from the greatly enhanced diffusion and transfer properties of charge carriers in the cells as a result of the improved quality of the OTP films. Our work presents an effective and useful strategy to fabricate high-performance planar heterojunction solar cells based on OTP materials. © The Royal Society of Chemistry 2016.


Lin T.,Nanjing University | Lin T.,Nanjing Medical University | Wu J.,Nanjing University | Wu J.,Jiangsu Key Laboratory for Nano Technology | And 8 more authors.
Journal of Pharmaceutical Sciences | Year: 2014

Drug solution is commonly used in conventional intravesical instillation. However, most of them would be easily eliminated by voiding, which significantly limit their efficacy. Recent advances in intravesical drug delivery are to use hydrogels as drug reservoir to extend the drug residence time in bladder. However, because of the high viscosity of hydrogel, urinary obstruction is usually existed during the intravesical instillation. To overcome these, we developed a floating hydrogel for the delivery of Adriamycin (ADR). The floating hydrogel was made of ADR, thermosensitive polymer (Poloxamer 407) and NaHCO3, which was liquid at low temperature, whereas formed gel at high temperature. In the presence of H+, NaHCO3 decomposed and produced CO2 that attached on the surface of hydrogel and helped the hydrogel float on the urine. Hence, the urinary tract will not be blocked. Meanwhile, the encapsulated ADR released in a controlled manner. These results suggest that the floating gel may have promising applications in intravesical therapy for bladder cancer. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.


Lin T.,Nanjing University | Lin T.,Nanjing Medical University | Zhang Y.,Nanjing University | Wu J.,Nanjing University | And 7 more authors.
Pharmaceutical Research | Year: 2014

Aim: Intravesical instillation is commonly used to decrease the tumor recurrence after transurethral resection. However, most drug solutions would be eliminated from bladder after the first voiding of urine, so its clinical efficacy is limited. To overcome this obstacle, we developed a floating hydrogel system for controlled delivery of antitumor drugs.Methods: The floating hydrogel was made of Adriamycin, thermo-sensitive polymer (Poloxamer 407) and NH4HCO3, which was liquid at low temperature while forming hydrogel at high temperature. Meanwhile, at high temperature, NH4HCO3 decomposed to produce CO2 bubbles, which helped hydrogel float in bladder without urinary obstruction.Results: The mixture containing 45% P407 and 6% NH4HCO3 was selected as the optimal formulation. At 37°C, the mixture formed hydrogel and produced many bubbles which could be observed by B ultrasound. The vitro study showed that the antitumor drug Doxorubicin was released in a controlled manner. After the mixture was instilled into rabbit bladder, it formed hydrogel and floated in the bladder. The bladder stimuli was reduced and antitumor drugs could be released continuously in the bladder.Conclusion: Our results suggested that the floating hydrogel was a feasible intravesical drug delivery system and may have application prospects in intravesical therapy for bladder cancer. © 2014 Springer Science+Business Media New York.


Fu G.,Nanjing University | Fu G.,Jiangsu Key Laboratory for Nano Technology | Yan S.,Nanjing University | Yan S.,Jiangsu Key Laboratory for Nano Technology | And 4 more authors.
Applied Physics Letters | Year: 2015

A key route to improving the performance of Ta3N5 photoelectrochemical film devices in solar driving water splitting to hydrogen is to understand the nature of the serious recombination of photo-generated carriers. Here, by using the temperature-dependent photoluminescence (PL) spectrum, we confirmed that for the Ta3N5 films prepared by nitriding Ta2O5 precursor, one PL peak at 561 nm originates from deep-level defects recombination of the oxygen-enriched Ta3N5 phases, and another one at 580 nm can be assigned to band recombination of Ta3N5 itself. Both of the two bulk recombination processes may decrease the photoelectrochemical performance of Ta3N5. It was difficult to remove the oxygen-enriched impurities in Ta3N5 films by increasing the nitriding temperatures due to their high thermodynamically stability. In addition, a broadening PL peak between 600 and 850 nm resulting from oxygen related surface defects was observed by the low-temperature PL measurement, which may induce the surface recombination of photo-generated carriers and can be removed by increasing the nitridation temperature. Our results provided direct experimental evidence to understand the effect of oxygen-related crystal defects in Ta3N5 films on its photoelectric performance. © 2015 AIP Publishing LLC.


Zhou P.,National Renewable Energy Laboratory | Gao H.L.,Nanjing University | Yan S.C.,Nanjing University | Yan S.C.,Jiangsu Key Laboratory for Nano Technology | And 3 more authors.
Dalton Transactions | Year: 2016

Functional hollow nanomaterials are of great interest due to their unique physical-chemical properties. Oxynitride photocatalysts are a kind of promising material for solar energy conversion. However, nanoscale design of hollow oxynitrides was difficult to achieve due to the thermal instability of oxide precursors at high temperature. Here, single crystal zinc gallium oxynitride nanotubes were successfully synthesized via the Kirkendall effect with ZnO nanorods and Ga2O3 nanosheets as precursors, which can be attributed to the high diffusion rate of ZnO and the high melting point of oxynitride. Enhanced photocatalytic performance in CO2 reduction was achieved over the as-prepared ZnGaNO nanotubes, due to their higher specific surface area and less recombination of the photogenerated carriers. These results are expected to provide new guidance in the design and preparation of highly efficient nano-scaled oxynitride photocatalysts. © The Royal Society of Chemistry 2016.


Zhu W.,National Renewable Energy Laboratory | Bao C.,National Renewable Energy Laboratory | Li F.,National Renewable Energy Laboratory | Zhou X.,National Renewable Energy Laboratory | And 7 more authors.
Chemical Communications | Year: 2015

A dense and homogenous flat wide-bandgap (1.75 eV) CH3NH3PbI2.1Br0.9 perovskite film was prepared via a facile halide exchange route. The planar-heterojunction solar cell shows an optimal power conversion efficiency of 12.67% with negligible current hysteresis due to the film's large grains and vertically oriented grain boundaries. © 2015 The Royal Society of Chemistry.

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