The “zeroth” scientific research challenge is what we call overarching and spillover research.

“Overarching” research is what connects the six main scientific research challenges to SSL technology. SSL technology is itself evolving rapidly, and we devote some effort to understanding this evolution so as to provide guidance for the directions of our inquiry to surmount the six scientific research challenges. For example, we have looked into

  • the question of the maximum white luminous efficacy of radiation possible for various combinations of color rendering index and color temperature- to better understand what wavelengths are ideal for SSL and therefore what materials and heterostructure (the interface between two layers of regions of dissimilar semiconducting materials that have unequal bandgaps architectures on which to focus our scientific attention;
  • how “tunable” quantum-dot absorption and quantum yields must be to make an impact on chromaticity tuned SSL- a likely important aspect of smart, ultra-efficient future SSL; and
  • the economics of lighting consumption- to better understand the energy savings and human productivity potential of various quantitative improvements in SSL production and usage efficiency.

“Spillover” research is related to unexpected phenomena which we occasionally come across during the course of our working in our six scientific research challenges. If it is not a major detour, and we see scientific benefit, we take advantage of the opportunity to dig a bit into the phenomena. In one example, we have been studying, in Scientific Research Challenge 6, the possibility of using stimulated emission, or lasing for SSL. This led us to apply the emerging fabrication techniques developed in Scientific Research Challenge 1 to fabricate and study nanowire lasers. Along the way, we discovered that these nanowire lasers can be tailored and manipulated to lase in a single transverse and single longitudinal optical mode. Because this phenomenon has major potential value in other applications for which energy efficiency is important, such as communications and displays, we have been looking more carefully at the conditions for such single mode lasing. En route, we also anticipate understanding more fully the conditions for ultra-high efficiency, which will be of interest to SSL.

Research Challenge Publications

  • Hung, Po-Chieh; and Tsao, Jeffrey Y. Maximym white luminous efficacy of radiation versus color rendering index and color temperature: Exact results and a useful analytic expression, J. Disp. Technol., (2012). [10.1109/JDT.2012.2224638]
  • Saunders, Harry D.; and Tsao, Jeffrey Y. Rebound effects for lighting, Energy Policy, 49, 477 (2012). [10.1016/j.enpol.2012.06.050]
  • Haitz, Roland; and Tsao, Jeffrey Y. ‘The Case’ Ten Years After and Future Prospects, Phys. Status Solidi A, 208, 17 (2011). [10.1002/pssa.201190000]
  • Tsao, Jeffrey Y.; Saunders, Harry D.; Creighton, J. Randall; Coltrin, Michael E.; and Simmons, Jerry A. Solid-State Lighting: An Energy Economics Perspective, J. Phys. D, 43, 354001 (2010). [10.1088/0022-3727/43/35/354001]
  • Tsao, Jeffrey Y.; and Waide, P. The World’s Appetite for Light: Empirical Data and Trends Spanning Three Centuries and Six Continents, Leukos, 6, 259-81 (2010). [10.1582/LEUKOS.2010.06.04001]
  • Tsao, Jeffrey Y.; Brener, Igal; Kelley, David F.; and Lyo, S. Ken Quantum-Dot-Based Solid-State Lighting With Electric-Field-Tunable Chromaticity, J. Disp. Technol., (2012). [10.1109/JDT.2012.2225407]
  • Ma, Ming; Cho, Jaehee; Schubert, E. Fred; Park, Yongjo; Kim, Gi Bum; and Sone, Cheolsoo Strong light-extraction enhancement in GaInN light-emitting diodes patterned with TiO2 micro-pillars with tapered sidewalls, Applied Physics Letters, 101, 141105 (2012). [10.1063/1.4756797]
  • Ma, Ming; Meyaard, David S.; Shan, Qifeng; Cho, Jaehee; Schubert, E. Fred; Kim, Gi Bum; Kim, Min-Ho; and Sone, Cheolsoo Polarized light emission from GaInN light-emitting diodes embedded with subwavelength aluminum wire-grid polarizers, Applied Physics Letters, 101, 061103 (2012). [10.1063/1.4744422]
  • Mont, Frank W.; Fischer, Arthur J.; Noemaun, A. N.; Poxson, David J.; Cho, Jaehee; Schubert, E. Fred; Crawford, Mary H.; Koleske, Daniel D.; and Fullmer, Kristine W. Enhanced light-extraction from a GaN waveguide using micro-pillar TiO2–SiO2 graded-refractive-index layers, Phys. Status Solidi A, 209, 2277 (2012). [10.1002/pssa.201228295]
  • Ma, Ming; Noemaun, A. N.; Cho, Jaehee; Schubert, E. Fred; Kim, Gi Bum; and Sone, Cheolsoo Emission pattern control and polarized light emission through patterned graded-refractiveindex coatings on GaInN light-emitting diodes, Optics Express, 20, 16677 (2012). [10.1364/OE.20.016677]
  • Li, Qiming; Figiel, Jeffrey J. ; Wang, George T.; Xu, Huiwen; and Balakrishnan, Ganesh GaN epitaxy on Cu(111) by metal organic chemical vapor deposition, Applied Physics Letters, 100, 192110 (2012). [10.1063/1.4714738]
  • Wierer, Jonathan J.; Li, Qiming; Koleske, Daniel D.; Lee, Stephen R. ; and Wang, George T. III-nitride core-shell nanowire arrayed solar cells, Nanotechnology, 23, 194007 (2012). [10.1088/0957-4484/23/19/194007]
  • Zhu, Di; Schubert, Martin F.; Xu, Jiuru; Cho, Jaehee; Schubert, E. Fred; Crawford, Mary H.; and Koleske, Daniel D. Genetic algorithm for innovative designs in high efficiency III-V nitride light-emitting diodes, Applied Physics Express, 5, 012102 (2012). [10.1143/APEX.5.012102]
  • Xu, Jiuru; Schubert, Martin F.; Zhu, Di; Cho, Jaehee; Schubert, E. Fred; Shim, Hyunwook; and Sone, Cheolsoo Effects of plarization-field tuning in GaInN light-emitting diodes, Applied Physics Letters, 99, 041105 (2011). [10.1063/1.3609783]
  • Neumann, Alexander; Wierer, Jonathan J.; Davis, Wendy; Ohno, Yoshi; Brueck, Steve R. J. ; and Tsao, Jeffrey Y. Four-color laser white illuminant demonstrating high color-rendering quality, Optics Express, 19, A982-A990 (2011). [10.1364/OE.19.00A982]
  • Lin, Guan-Bo; Schubert, Martin F.; Cho, Jaehee; Schubert, E. Fred; and Kim, Hyungkun A complementary matching technique to reduce the variance of optical and electrical properties of light-emitting diodes, Journal of the Society for Information Display, 19, 431 (2011). [10.1889/JSID19.6.431]
  • Shelton, David J.; Brener, Igal; Ginn, James C.; Sinclair, Michael B.; Peters, David W.; Coffey, Kevin R.; and Boreman, Glenn D. Strong Coupling between Nanoscale Metamaterials and Phonons, Nano Lett.,, 11, 2104-2108 (2011). [10.1021/nl200689z]