Bio

B.E. ​Cooper Union, 2006​Ph.D. Cornell University, 2012Post-Doc ​Columbia University, 2012 - 2014

"Our research enables development of novel hybrid organic-inorganic materials with tailored properties for next generation optoelectronic devices."

Joshua J. Choi, Assistant Professor

Joshua J. Choi received B.E. in Chemical Engineering from Cooper Union and Ph.D. in Applied Physics from Cornell University. He then performed postdoctoral research at the Department of Chemistry, Columbia University. He joined the faculty of the Department of Chemical Engineering, University of Virginia as an assistant professor starting in August, 2014. He is a recipient of a NASA Early Career Faculty Award (2015).

 

At the nanoscale, quantum mechanical effects and various other mechanisms cause the properties of semiconductors to strongly depend on the size, shape and surface of the material. For example, when the size of a semiconductor crystal becomes smaller than the size of electronic wave function (typically few to tens of nanometers in semiconductors), manipulating the spatial extension of the carrier wave function becomes possible simply by changing the size of the crystal. This 'wave function engineering' gives rise to intriguing cases where, depending on the size of the crystal, semiconductors with the identical composition can have drastically different band gaps, carrier-carrier Coulomb interaction strengths and excited state dynamics. In addition to the size-tunability, properties of semiconductor nanomaterials can be manipulated by forming hetero-nanostructures with other semiconductors, metals and organic molecules as well as tuning their collective interactions within their assemblies. This extremely wide tunability in properties of semiconductor nanomaterials presents many intriguing scientific questions and unique opportunities for transformative advances in technological applications. 

Currently, our research group is focused on studying metal-organic perovskites and colloidal quantum dots - both material systems exhibit intriguing properties tunable by design while looking set to revolutionize the field of solution processed optoelectronic devices. We are developing novel and advanced synthetic methods to achieve robust heterostructure formation, surface structure and impurity doping. We seek to understand and control the structure-property relationships in these materials. To this end, we employ a wide variety of techniques, including synchrotron based X-ray diffraction methods, to study their structure and self-assembly behavior from atomic to macroscopic length scales. We also employ optical spectroscopy and electrical transport measurement techniques to examine properties of the materials as functions of their structure. Newly obtained insights are applied to fabrication and testing of prototype devices to demonstrate improved performance. Particularly, our efforts will be focused on solution processing based device fabrication methods to simultaneously achieve a low-cost and high performance required for wide spread commercial deployment.

Awards

  • NASA Early Career Faculty Award 2015
  • VSGC New Investigator Award 2015

Research Interests

  • Materials Chemistry
  • Optoelectronic Devices
  • Solar Power
  • Nanomaterials and nanomanufacturing
  • Nanoelectronics and 2-D Materials

Selected Publications

  • "Origin of vertical orientation in two-dimensional metal halide perovskites and its effect on photovoltaic performance" Nature Communications, 9, 1336 (2018) (*corresponding author) ABS A. Z. Chen, M. Shiu, J. H. Ma, M. R. Alpert, D. Zhang, B. J. Foley, D.-M. Smilgies, S.-H. Lee and J. J. Choi*
  • "Room Temperature Processing of TiOx Electron Transporting Layer for Perovskite Solar Cells" The Journal of Physical Chemistry Letters, 8, 3206–3210 (2017) ABS X. Deng, G. C. Wilkes, A. Z. Chen, N. S. Prasad, M. C. Gupta*, and J. J. Choi*
  • "Origin of long lifetime of band-edge charge carriers in organic–inorganic lead iodide perovskites" Proceedings of the National Academy of Sciences, 114, 7519-7524 (2017) ABS T. Chen, W.-L. Chen, B. J. Foley, J. Lee, J. P. C. Ruff, J. Y. P. Ko, C. M. Brown, L. W Harriger, D. Zhang, C. Park, M. Yoon, Y.-M. Chang, J. J. Choi* and S.-H. Lee*
  • "Improved Charge Collection in Highly Efficient CsPbBrI2 Solar Cells with Light-Induced Dealloying" ACS Energy Letters 2, 1043-1049 (2017) ABS J. S. Niezgoda, B. J. Foley, A. Z. Chen and J. J. Choi*
  • "Crystallographic orientation propagation in metal halide perovskite thin films" Journal of Materials Chemistry A, 5, 7796-7800 (2017) ABS A. Z. Chen, B. J. Foley, J. H. Ma, M. R. Alpert, J. S. Niezgoda and J. J. Choi*
  • “Controlling Nucleation, Growth, and Orientation of Metal Halide Perovskite Thin Films with Rationally Selected Additives” Journal of Materials Chemistry A, 5, 113 - 123 (2017) ABS B. J. Foley, J. Girard, B. A. Sorenson, A. Z. Chen, J. S. Niezgoda, M. R. Alpert, A. F. Harper, D.-M. Smilgies,P. Clancy, W. A. Saidi, and J. J. Choi*
  • “Entropy Driven Structural Transition and Kinetic Trapping in Formamidinium Lead Iodide Perovskite” Science Advances, 2, e1601650 (2016) ABS T. Chen, B. J. Foley, C. Park, C. M. Brown, L. W. Harriger, J. Lee, J. Ruff, M. Yoon, J. J. Choi*, and S.-H. Lee*
  • "Rotational Dynamics of Organic Cations in CH3NH3PbI3 Perovskite", Physical Chemistry Chemical Physics, 17, 31278 - 31286 (2015) ABS T. Chen, B. J. Foley, B. Ipek, M. Tyagi, J. R. D. Copley, C. M. Brown, J. J. Choi* and S.-H. Lee*
  • “Temperature Dependent Energy Levels of Methylammonium Lead Iodide Perovskite” Applied Physics Letters, 106, 243904 (2015) ABS B. J. Foley, D. L. Marlowe, K. Sun, W. A. Saidi, L. Scudiero*, M. C. Gupta* and J. J. Choi*