Hanying Li

Zhejiang University, Hang-hsien, Zhejiang Sheng, China

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Publications (27)193.19 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Organic single crystals are ideal candidates for high-performance photovoltaics due to their high charge mobility and long exciton diffusion length; however, they have not been largely considered for photovoltaics due to the practical difficulty in making a heterojunction between donor and acceptor single crystals. Here, we demonstrate that extended single-crystalline heterojunctions with a consistent donor-top and acceptor-bottom structure throughout the substrate can be simply obtained from a mixed solution of C60 (acceptor) and 3,6-bis(5-(4-n-butylphenyl)thiophene-2-yl)-2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4-dione (donor). 46 photovoltaic devices were studied with the power conversion efficiency of (0.255±0.095) % under 1 sun, which is significantly higher than the previously reported value for a vapor-grown organic single-crystalline donor–acceptor heterojunction (0.007 %). As such, this work opens a practical avenue for the study of organic photovoltaics based on single crystals.
    Angewandte Chemie 11/2014;
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    ABSTRACT: Achieving superior solar cell performance based on the colloidal nanocrystals remains challenging due to their complex surface composition. Much attention has been devoted to the development of effective surface modification strategies to enhance electronic coupling between the nanocrystals to promote charge carrier transport. Herein, we aim to attach benzenedithiol ligands onto the surface of CdSe nanocrystals in the "face-on" geometry to minimize the nanocrystal-nanocrystal or polymer-nanocrystal distance. Furthermore, the "electroactive" π-orbitals of the benzenedithiol are expected to further enhance the electronic coupling, which facilitates charge carrier dissociation and transport. The electron mobility of CdSe QD films was improved 20 times by tuning the ligand orientation, and high performance poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT):CdSe nanocrystal hybrid solar cells were also achieved, showing a highest power conversion efficiency of 4.18%. This research could open up a new pathway to improve further the performance of colloidal nanocrystal based solar cells.
    ACS Applied Materials & Interfaces 10/2014; · 5.90 Impact Factor
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    ABSTRACT: Cadmium selenide (CdSe) nanocrystal was used as electron transport/extraction layer for perovskite solar cells due to its high electron mobility and solution-processing ability at low temperature. Power conversion efficiency (PCE) up to 11.7% was achieved under standard AM 1.5G conditions in air.
    J. Mater. Chem. C. 09/2014;
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    ABSTRACT: Effects of molecular dipole at the conjugated polymer/nanocrystal interface on the energy level alignment, exciton dissociation process, and consequently the photovoltaic performance of poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT):CdSe quantum dots bulk heterojunction hybrid solar cells are systemically studied. Power conversion efficiency up to 4.0% is achieved when 4-fluorobenzenethiol is used for ligand exchange.
    Nanoscale 07/2014; · 6.73 Impact Factor
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    ABSTRACT: Biogenic single-crystals have been found to incorporate biomacromolecules and become biomacromolecule/single-crystal composites. The complex composite structures and properties of these biogenic crystalline materials have spurred investigations to reproduce their synthetic analogs, polymer/single-crystal composites. Here, we review recent progress of the synthetic polymer/single-crystal composites, where the polymers are distributed inside the crystals in their aggregate states (micelles, particles, gel networks, and 3D structured forms). The mechanisms of the polymer incorporation are also discussed. Furthermore, the effects of the polymer incorporation on the properties of the crystal host are described. Copyright © 2014 John Wiley & Sons, Ltd.
    Polymers for Advanced Technologies 06/2014; · 1.64 Impact Factor
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    ABSTRACT: Single crystals of C60 have been widely prepared previously. However, their electronic properties are much less frequently studied, although C60 is known as an outstanding electronic material. Also, the reported electron mobility values (10−2 cm2 V−1 s−1) of C60 single-crystals are unexpectedly low possibly due to the difficulties in the fabrication of single-crystal devices. We have recently reported a droplet receding method for the solution-grown C60 single-crystals with mobilities above 1 cm2 V−1 s−1. In this work, we systematically investigate the effects of solvent and surface properties of the substrate on the growth of C60 single-crystals. Well-aligned C60 needle-like and ribbon-like single-crystals were grown from suitable solvents (m-xylene or a mixed solvent of m-xylene and carbon tetrachloride) conformally on the field-effect transistor (FET) substrates that were wet well by the receding droplet. Based on the ribbon-like single-crystals, an average electron mobility of 2.0 ± 0.61 cm2 V−1 s−1, Ion/Ioff > 106, and a VT between 36 and 85 V were achieved from 60 field-effect transistors. Insights provided by this work may help accelerate the development of solution-grown single-crystals of organic semiconductors.
    J. Mater. Chem. C. 04/2014; 2(18).
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    ABSTRACT: Synthetic single crystals are usually homogeneous solids. Biogenic single crystals, however, can incorporate biomacromolecules and become inhomogeneous solids so that their properties are also extrinsically regulated by the incorporated materials. The discrepancy between the properties of synthetic and biogenic single crystals leads to the idea to modify the internal structure of synthetic crystals to achieve nonintrinsic properties by incorporation of foreign material. Intrinsically colorless and diamagnetic calcite single crystals are turned into colored and paramagnetic solids, through incorporation of Au and Fe3O4 nanoparticles without significantly disrupting the crystalline lattice of calcite. The crystals incorporate the nanoparticles and gel fibers when grown in agarose gel media containing the nanoparticles, whereas the solution-grown crystals do not. As such, our work extends the long-history gel method for crystallization into a platform to functionalize single-crystalline materials.
    Angewandte Chemie International Edition 03/2014; · 11.34 Impact Factor
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    ABSTRACT: Formation of S-shaped I–V curve or the so-called kink has been shown detrimental to organic solar cells (OSC) performance. Previous researches have indicated that a variety of reasons could count for the origin of the S-shaped I–V curve. However, its origin is still not clear. In this contribution, we investigated the origin of S-shaped I–V curve from the view of an equivalent circuit model (ECM) in OSCs. The proposed ECM involves a rectifying junction connected with a donor/accepter (D/A) junction in series. OSCs with and without a Schottky barrier that was a rectifying junction were fabricated to verify the modeled results. And the good reproduction of experimental results confirmed the validity of our model. The results indicate that the origin of S-shaped I–V curve in OSCs is associated with the rectifying junction. With this model, the effects of the rectifying junction on the shape of I–V characteristic and its effect on device parameters are analyzed: fill factor (FF) dropped, short circuit current density decreased, open circuit voltage however, remained. Also, from simulation, we varied the parameters of the rectifying junction to study their influence on the device performance.
    Solar Energy Materials and Solar Cells 03/2014; 122:88–93. · 5.03 Impact Factor
  • Advanced Materials Interfaces 02/2014;
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    ABSTRACT: Organic single-crystalline p-n junctions are grown from mixed solutions. First, C60 crystals (n-type) form and, subsequently, C8-BTBT crystals (p-type) nucleate heterogeneously on the C60 crystals. Both crystals continue to grow simultaneously into single-crystalline p-n junctions that exhibit ambipolar charge transport characteristics. This work provides a platform to study organic single-crystalline p-n junctions.
    Advanced Materials 08/2013; · 14.83 Impact Factor
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    ABSTRACT: High-mobility organic field-effect transistors (OFETs) are the basic units for a variety of high-performance electronic applications. Here, we review recent progress in controlling molecular packing and crystal growth in high-mobility, small molecular organic FETs. Strategies to tune molecular packing of organic semiconductors and their impact on charge transport are described. Methods for the controlled growth of single-crystal organic semiconductors required for large-area device construction are reviewed. Furthermore, the advantages, limitations, and potential of these methods are also discussed.
    MRS Bulletin. 01/2013; 38(01).
  • Organic Electronics 11/2012; 13(11):2450–2460. · 3.84 Impact Factor
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    ABSTRACT: The crystalline film growth of TIPS-pentacene thin films by confined solution deposition is investigated. The crystalline thin films grow dendritic in the initial stage and continue to grow to elongated plate-like crystals when the solution is deposited in a confined space in-plane. The majority of the thin film, containing smaller thin crystals, is formed within the first 10 s after depositing the solution and continues to grow in minutes to millimeter sized single crystals. By atomic force microscopy we show that impurities are expelled by the growing crystals and clusters accumulate at step edges on the surface of the larger crystals. The influence of crystal thickness and orientation on the electronic transport in field-effect transistors is studied, and shows an optimum performance for devices with thin elongated crystals that are aligned parallel to the electric field between the source–drain electrodes.
    Organic Electronics 10/2012; 13(10):2056–2062. · 3.84 Impact Factor
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    ABSTRACT: This paper reports how the morphology of a polymer–fullerene derivative blend is tuned via the different aggregate states of the polymer in solutions. Based on a copolymer with benzodiothiophene and thiophene-3-carboxylate as alternating units (PBDTCT), we explored the polymer aggregation (i.e., organo-gels) behavior as a function of steric hindrance of aromatic solvents imposed by substituents. We showed that the size of organo-gels decreased as the substituents of solvents got larger. Also, the phase separation and domain size of the subsequent spin-coated films increased monotonically with that of the organo-gels in solution. Through this knowledge, we eventually achieve controlled morphology and optimized organic solar cells (OSCs) performance. Our results present a significant step forward for understanding the self-assembly behavior of conjugated polymers, control of their morphology and optimization of OSC performance.
    The Journal of Physical Chemistry C 08/2012; 116(32):16893. · 4.84 Impact Factor
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    ABSTRACT: Various semiconductors have been studied as photocatalysts for photocatalytic degradation of pollutants in aqueous solutions. As one of the promising visible-light-driven semiconductor photocatalysts, α-Fe(2)O(3) has advantages of low cost and stability. However, its application is inhibited by the poor separation of photogenerated electron-hole pair. In this work, hybrid structures were prepared to improve the performance of α-Fe(2)O(3). CdS nanoparticles were overgrown on the preformed single-crystalline α-Fe(2)O(3) nanorods by a simple and mild one-step wet-chemical method, resulting in α-Fe(2)O(3)/CdS cornlike nanocomposites. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy showed the α-Fe(2)O(3)/CdS core/shell heterostructure of the nanocomposite with high crystallinity. Furthermore, the cornlike nanocomposites exhibited superior photocatalytic performances under visible light irradiation over the pure α-Fe(2)O(3) nanorods and CdS nanoparticles. The photocatalytic activity of the composites is superior to the previously-reported pure α-Fe(2)O(3) nanomaterials, and the performance is comparable to both the commercial TiO(2) (P25) which is used under UV irradiation and the newly developed α-Fe(2)O(3)/SnO(2) photocatalyst under visible light irradiation. The enhanced performance is associated with the larger surface area of the cornlike structure, the crystalline nature of the materials and the synergy in light absorption and charge separation between α-Fe(2)O(3) and CdS. As such, our α-Fe(2)O(3)/CdS cornlike nanocomposites may be promising to be used as visible-light-driven high-performance photocatalyst.
    ACS Applied Materials & Interfaces 08/2012; 4(9):4800-6. · 5.90 Impact Factor
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    ABSTRACT: High-performance hybrid solar cells (HSCs) based on P3HT : CdSe QD blends are achieved through post-deposition ligand exchange by n-butanethiol (n-BT) with a high power conversion efficiency of 3.09%. The mechanism by which n-BT modifies the surface structures of CdSe QDs and thus improves the HSCs performance is investigated.
    Physical Chemistry Chemical Physics 08/2012; 14(35):12094-8. · 4.20 Impact Factor
  • Advanced Functional Materials 07/2012; 22(14). · 10.44 Impact Factor
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    ABSTRACT: In recent years, the prevalence of hydrogel-like organic matrices in biomineralization has gained attention as a route to synthesizing a diverse range of crystalline structures. Here, examples of hydrogels in biological, as well as synthetic, bio-inspired systems are discussed. Particular attention is given to understanding the physical versus chemical effects of a broad range of hydrogel matrices and their role in directing polymorph selectivity and morphological control in the calcium carbonate system. Finally, recent data regarding hydrogel-matrix incorporation into the growing crystals is discussed and a mechanism for the formation of these single-crystal composite materials is presented.
    Advanced Functional Materials 07/2012; 22(14). · 10.44 Impact Factor
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    ABSTRACT: Well-aligned C(60) and TIPS-pentacene single-crystals grow on a common substrate by a droplet-pinned crystallization method. Complementary inverters based on the two aligned crystals show gain values as high as 155. This work demonstrates a simple solution-processing approach to investigate high-performance complementary circuits based on organic single-crystals.
    Advanced Materials 03/2012; 24(19):2588-91. · 14.83 Impact Factor
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    ABSTRACT: Field-effect transistors based on single crystals of organic semiconductors have the highest reported charge carrier mobility among organic materials, demonstrating great potential of organic semiconductors for electronic applications. However, single-crystal devices are difficult to fabricate. One of the biggest challenges is to prepare dense arrays of single crystals over large-area substrates with controlled alignment. Here, we describe a solution processing method to grow large arrays of aligned C(60) single crystals. Our well-aligned C(60) single-crystal needles and ribbons show electron mobility as high as 11 cm(2)V(-1)s(-1) (average mobility: 5.2 ± 2.1 cm(2)V(-1)s(-1) from needles; 3.0 ± 0.87 cm(2)V(-1)s(-1) from ribbons). This observed mobility is ~8-fold higher than the maximum reported mobility for solution-grown n-channel organic materials (1.5 cm(2)V(-1)s(-1)) and is ~2-fold higher than the highest mobility of any n-channel organic material (~6 cm(2)V(-1)s(-1)). Furthermore, our deposition method is scalable to a 100 mm wafer substrate, with around 50% of the wafer surface covered by aligned crystals. Hence, our method facilitates the fabrication of large amounts of high-quality semiconductor crystals for fundamental studies, and with substantial improvement on the surface coverage of crystals, this method might be suitable for large-area applications based on single crystals of organic semiconductors.
    Journal of the American Chemical Society 02/2012; 134(5):2760-5. · 10.68 Impact Factor

Publication Stats

136 Citations
193.19 Total Impact Points

Institutions

  • 2012–2014
    • Zhejiang University
      • State Key Lab of Silicon Materials
      Hang-hsien, Zhejiang Sheng, China
    • Stanford University
      • Department of Chemical Engineering
      Stanford, CA, United States
  • 2007–2012
    • Cornell University
      • Department of Materials Science and Engineering
      Ithaca, New York, United States