Professional Education


  • Doctor of Philosophy, Nanjing University (2014)
  • Bachelor of Science, Nanjing University (2009)
  • Master of Science, Nanjing University (2011)

Stanford Advisors


All Publications


  • Highly stretchable polymer semiconductor films through the nanoconfinement effect SCIENCE Xu, J., Wang, S., Wang, G. N., Zhu, C., Luo, S., Jin, L., Gu, X., Chen, S., Feig, V. R., To, J. W., Rondeau-Gagne, S., Park, J., Schroeder, B. C., Lu, C., Oh, J. Y., Wang, Y., Kim, Y., Yan, H., Sinclair, R., Zhou, D., Xue, G., Murmann, B., Linder, C., Cai, W., Tok, J. B., Chung, J. W., Bao, Z. 2017; 355 (6320): 59-?

    Abstract

    Soft and conformable wearable electronics require stretchable semiconductors, but existing ones typically sacrifice charge transport mobility to achieve stretchability. We explore a concept based on the nanoconfinement of polymers to substantially improve the stretchability of polymer semiconductors, without affecting charge transport mobility. The increased polymer chain dynamics under nanoconfinement significantly reduces the modulus of the conjugated polymer and largely delays the onset of crack formation under strain. As a result, our fabricated semiconducting film can be stretched up to 100% strain without affecting mobility, retaining values comparable to that of amorphous silicon. The fully stretchable transistors exhibit high biaxial stretchability with minimal change in on current even when poked with a sharp object. We demonstrate a skinlike finger-wearable driver for a light-emitting diode.

    View details for DOI 10.1126/science.aah4496

    View details for Web of Science ID 000391739900042

    View details for PubMedID 28059762

  • Low-temperature processing of polymer nanoparticles for bioactive composites JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS Li, X., Xu, J., Wang, D., Sha, Y., Chen, W., Zhou, D., Wang, X., Sun, Q., Xue, G., Li, L. 2016; 54 (24): 2514-2520

    View details for DOI 10.1002/polb.24253

    View details for Web of Science ID 000387117500007

  • Intrinsically stretchable and healable semiconducting polymer for organic transistors NATURE Oh, J. Y., Rondeau-Gagne, S., Chiu, Y., Chortos, A., Lissel, F., Wang, G. N., Schroeder, B. C., Kurosawa, T., Lopez, J., Katsumata, T., Xu, J., Zhu, C., Gu, X., Bae, W., Kim, Y., Jin, L., Chung, J. W., Tok, J. B., Bao, Z. 2016; 539 (7629): 411-415

    Abstract

    Thin-film field-effect transistors are essential elements of stretchable electronic devices for wearable electronics. All of the materials and components of such transistors need to be stretchable and mechanically robust. Although there has been recent progress towards stretchable conductors, the realization of stretchable semiconductors has focused mainly on strain-accommodating engineering of materials, or blending of nanofibres or nanowires into elastomers. An alternative approach relies on using semiconductors that are intrinsically stretchable, so that they can be fabricated using standard processing methods. Molecular stretchability can be enhanced when conjugated polymers, containing modified side-chains and segmented backbones, are infused with more flexible molecular building blocks. Here we present a design concept for stretchable semiconducting polymers, which involves introducing chemical moieties to promote dynamic non-covalent crosslinking of the conjugated polymers. These non-covalent crosslinking moieties are able to undergo an energy dissipation mechanism through breakage of bonds when strain is applied, while retaining high charge transport abilities. As a result, our polymer is able to recover its high field-effect mobility performance (more than 1 square centimetre per volt per second) even after a hundred cycles at 100 per cent applied strain. Organic thin-film field-effect transistors fabricated from these materials exhibited mobility as high as 1.3 square centimetres per volt per second and a high on/off current ratio exceeding a million. The field-effect mobility remained as high as 1.12 square centimetres per volt per second at 100 per cent strain along the direction perpendicular to the strain. The field-effect mobility of damaged devices can be almost fully recovered after a solvent and thermal healing treatment. Finally, we successfully fabricated a skin-inspired stretchable organic transistor operating under deformations that might be expected in a wearable device.

    View details for DOI 10.1038/nature20102

    View details for Web of Science ID 000388161700050

    View details for PubMedID 27853213

  • Inducing Elasticity through Oligo-Siloxane Crosslinks for Intrinsically Stretchable Semiconducting Polymers ADVANCED FUNCTIONAL MATERIALS Wang, G. N., Shaw, L., Xu, J., Kurosawa, T., Schroeder, B. C., Oh, J. Y., Benight, S. J., Bao, Z. 2016; 26 (40): 7254-7262
  • Combinatorial Study of Temperature-Dependent Nanostructure and Electrical Conduction of Polymer Semiconductors: Even Bimodal Orientation Can Enhance 3D Charge Transport ADVANCED FUNCTIONAL MATERIALS Park, S., Lee, M. H., Ahn, K. S., Choi, H. H., Shin, J., Xu, J., Mei, J., Cho, K., Bao, Z., Lee, D. R., Kang, M. S., Kim, D. H. 2016; 26 (26): 4627-4634
  • Non-Conjugated Flexible Linkers in Semiconducting Polymers: A Pathway to Improved Processability without Compromising Device Performance ADVANCED ELECTRONIC MATERIALS Schroeder, B. C., Chiu, Y., Gu, X., Zhou, Y., Xu, J., Lopez, J., Lu, C., Toney, M. F., Bao, Z. 2016; 2 (7)
  • Stretchable Self-Healing Polymeric Dielectrics Cross-Linked Through Metal-Ligand Coordination JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Rao, Y., Chortos, A., Pfattner, R., Lissel, F., Chiu, Y., Feig, V., Xu, J., Kurosawa, T., Gu, X., Wang, C., He, M., Chung, J. W., Bao, Z. 2016; 138 (18): 6020-6027

    Abstract

    A self-healing dielectric elastomer is achieved by the incorporation of metal-ligand coordination as cross-linking sites in nonpolar polydimethylsiloxane (PDMS) polymers. The ligand is 2,2'-bipyridine-5,5'-dicarboxylic amide, while the metal salts investigated here are Fe(2+) and Zn(2+) with various counteranions. The kinetically labile coordination between Zn(2+) and bipyridine endows the polymer fast self-healing ability at ambient condition. When integrated into organic field-effect transistors (OFETs) as gate dielectrics, transistors with FeCl2 and ZnCl2 salts cross-linked PDMS exhibited increased dielectric constants compared to PDMS and demonstrated hysteresis-free transfer characteristics, owing to the low ion conductivity in PDMS and the strong columbic interaction between metal cations and the small Cl(-) anions which can prevent mobile anions drifting under gate bias. Fully stretchable transistors with FeCl2-PDMS dielectrics were fabricated and exhibited ideal transfer characteristics. The gate leakage current remained low even after 1000 cycles at 100% strain. The mechanical robustness and stable electrical performance proved its suitability for applications in stretchable electronics. On the other hand, transistors with gate dielectrics containing large-sized anions (BF4(-), ClO4(-), CF3SO3(-)) displayed prominent hysteresis due to mobile anions drifting under gate bias voltage. This work provides insights on future design of self-healing stretchable dielectric materials based on metal-ligand cross-linked polymers.

    View details for DOI 10.1021/jacs.6b02428

    View details for Web of Science ID 000375889100044

    View details for PubMedID 27099162

  • Effect of Solution Shearing Method on Packing and Disorder of Organic Semiconductor Polymers CHEMISTRY OF MATERIALS Giri, G., Delongchamp, D. M., Reinspach, J., Fischer, D. A., Richter, L. J., Xu, J., Benight, S., Ayzner, A., He, M., Fang, L., Xue, G., Toney, M. F., Bao, Z. 2015; 27 (7): 2350-2359

    View details for DOI 10.1021/cm503780u

    View details for Web of Science ID 000353176100013

  • Understanding Polymorphism in Organic Semiconductor Thin Films through Nanoconfinement JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Diao, Y., Lenn, K. M., Lee, W., Blood-Forsythe, M. A., Xu, J., Mao, Y., Kim, Y., Reinspach, J. A., Park, S., Aspuru-Guzik, A., Xue, G., Clancy, P., Bao, Z., Mannsfeld, S. C. 2014; 136 (49): 17046-17057

    Abstract

    Understanding crystal polymorphism is a long-standing challenge relevant to many fields, such as pharmaceuticals, organic semiconductors, pigments, food, and explosives. Controlling polymorphism of organic semiconductors (OSCs) in thin films is particularly important given that such films form the active layer in most organic electronics devices and that dramatic changes in the electronic properties can be induced even by small changes in the molecular packing. However, there are very few polymorphic OSCs for which the structure-property relationships have been elucidated so far. The major challenges lie in the transient nature of metastable forms and the preparation of phase-pure, highly crystalline thin films for resolving the crystal structures and evaluating the charge transport properties. Here we demonstrate that the nanoconfinement effect combined with the flow-enhanced crystal engineering technique is a powerful and likely material-agnostic method to identify existing polymorphs in OSC materials and to prepare the individual pure forms in thin films at ambient conditions. With this method we prepared high quality crystal polymorphs and resolved crystal structures of 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene), including a new polymorph discovered via in situ grazing incidence X-ray diffraction and confirmed by molecular mechanic simulations. We further correlated molecular packing with charge transport properties using quantum chemical calculations and charge carrier mobility measurements. In addition, we applied our methodology to a [1]benzothieno[3,2-b][1]1benzothiophene (BTBT) derivative and successfully stabilized its metastable form.

    View details for DOI 10.1021/ja507179d

    View details for Web of Science ID 000346544200021

    View details for PubMedID 25333565

  • Probing the interfacial molecular packing in TIPS-pentacene organic semiconductors by surface enhanced Raman scattering JOURNAL OF MATERIALS CHEMISTRY C Xu, J., Diao, Y., Zhou, D., Mao, Y., Giri, G., Chen, W., Liu, N., Mannsfeld, S. C., Xue, G., Bao, Z. 2014; 2 (16): 2985-2991

    View details for DOI 10.1039/c3tc32581d

    View details for Web of Science ID 000334123800020

  • Solution coating of large-area organic semiconductor thin films with aligned single-crystalline domains. Nature materials Diao, Y., Tee, B. C., Giri, G., Xu, J., Kim, D. H., Becerril, H. A., Stoltenberg, R. M., Lee, T. H., Xue, G., Mannsfeld, S. C., Bao, Z. 2013; 12 (7): 665-671

    Abstract

    Solution coating of organic semiconductors offers great potential for achieving low-cost manufacturing of large-area and flexible electronics. However, the rapid coating speed needed for industrial-scale production poses challenges to the control of thin-film morphology. Here, we report an approach-termed fluid-enhanced crystal engineering (FLUENCE)-that allows for a high degree of morphological control of solution-printed thin films. We designed a micropillar-patterned printing blade to induce recirculation in the ink for enhancing crystal growth, and engineered the curvature of the ink meniscus to control crystal nucleation. Using FLUENCE, we demonstrate the fast coating and patterning of millimetre-wide, centimetre-long, highly aligned single-crystalline organic semiconductor thin films. In particular, we fabricated thin films of 6,13-bis(triisopropylsilylethynyl) pentacene having non-equilibrium single-crystalline domains and an unprecedented average and maximum mobilities of 8.1±1.2 cm(2) V(-1) s(-1) and 11 cm(2) V(-1) s(-1). FLUENCE of organic semiconductors with non-equilibrium single-crystalline domains may find use in the fabrication of high-performance, large-area printed electronics.

    View details for DOI 10.1038/nmat3650

    View details for PubMedID 23727951