Sudhir  

Sudhir Ranjan, Ph.D

Carnegie Mellon University
Department of Chemical Engineering
Doherty Hall, Room 3112
Pittsburgh, PA 15213

412-268-3039
sranjan@andrew.cmu.edu

Education History

1992 M.S, Chemistry,. Indian Institute of Technology, Delhi, India
1998 Ph.D, Chemistry, Indian Institute of Technology, Kanpur, India
Work History
2007- Post Doc Researcher, Chemical Engineering, Carnegie Mellon University, USA
2006-2007 Chemist, KMG2 Sensors Corp, State College, PA, USA
2004-2006 Researcher/Project Leader, Industrial Technology Research Institute, Hsinchu, Taiwan
2002-2003 Post Doc Researcher, Chemistry Department, University of Louisville, USA
1999-2002 Post Doc Research Associate, National Tsing Hua University, Hsinchu, Taiwan

 

Awards/Other Activities

  1. Placed First in the University of Bihar (B.S. program), Muzaffarpur (India)
  2. Joint University Grants Commission – Council of Scientific and Industrial Research (UGC-CSIR) National Level Fellowship: (1992-1997), India
  3. National Merit Scholarship (1984-1989), Bihar, India.
  4. Coordinated Lab. Courses for B.S. (CHM 101) and M.S. (CHM 443) at IIT, Kanpur, India.
  5. Member, American Chemical Society
Research Interests

Design and development of Solar Quality Silicon Sheet (or wafer)

Silicon solar cell is one of the matured and dominant amongst all solar cell technologies and is based on the use of Silicon wafers. Wafering is usually achieved by slicing ingots processed via Czochralski method (single crystalline) and various casting methods (multi-crystalline). Wires used to cut these ingots are as thick as wafers and hence, cutting crystals of any kind into slices is wasteful and expensive. Moreover, the quality and cost of Silicon wafers, in the case of most widely used multi-crystalline form; depend on the quality and cost of solidified ingots of Silicon and prevention of any reactions between highly reactive molten silicon and mold (or crucible) during casting process. Several other relatively less expensive methods, String Ribbon (SR), Edge-defined Film-fed crystal Growth (EFG), Molded Wafers (MW), Ribbon-Growth-on Substrate (RGS) and Crystalline Silicon on Glass (CSG) were explored to grow or cast silicon sheet (poly-crystalline/multi-crystalline) directly from silicon melt to rival the wire saw process on an industrial scale. Molds and/or mechanical supports are preferably made up of solid substrates such as silica, alumina, graphite or silicon carbide plus a coating of silicon nitride. Molten silicon cast on these involves directional solidification leading to multi-crystalline structure with numerous crystal defects.

Alternatively, we are developing and substituting the existing (mechanical) supports with novel substrates in order to directly cast a continuous solar quality silicon sheet (or wafer). Our process identifies and develops a new, substrate-assisted method of producing thin-sheet of Silicon. As shown in the figures below, it is possible to produce high purity Silicon <111> sheets.

silicon1silicon2

 

Further fundamental investigations of these issues involving both theoretical and experimental studies are in progress.

Following are the main topics of our interests in this area:

  1. High-temperature spreading and stabilized fluid flow
  2. Wetability, reactivity and in-situ observation of interfacial morphology of molten Silicon.
  3. Heat transfer processes and creation of self-aligned heat reservoir
  4. Conditions for crystal growth behavior
  5. Interactive solidification and crystallization

Publications

Book:

  1. Craig A. Grimes, Oomman K. Varghese, Sudhir Ranjan.Light, Water, Hydrogen: The Solar Generation of Hydrogen by Water Photoelectrolysis”. Springer, New York, USA, 2008 (First edition released on December 04, 2007).
    • Chapter 3: Photoelectrolysis, pp. 115-190
    • Chapter 4: Oxide Semiconductor Materials as Photoanodes, pp.191-256
    • Chapter 6: Oxide Semiconductors: Suspended Nanoparticle Systems, pp.371-426
    • Chapter 7: Non-oxide Semiconductors Nanostructures, pp. 427-484
    • Chapter 8: Photovoltaic-electrolysis Cells, pp. 485-516

Patent:

  1. B. Erik Ydstie, Sudhir Ranjan, Method of Casting by a Float Process and Associated Apparatuses. US Patent-patent Pending (2009)

 Research Papers (Selected):

  1. Sudhir Ranjan, Zhi-Feng Jue, Frank L. Chen. Multi-walled carbon nanotube/polymer composite: A nano-enabled continuous fiber. J. Compos. Mater. In Press (2010).
  2. Sudhir Ranjan, S.-Y. Lin, K.-C. Hwang, Y. Chi, W.-L. Ching, C.-S. Liu, Y.-T. Tao, C.-H. Chien, S. M. Peng, G.H. Lee. Realizing green phosphorescent light-emitting materials from rhenium(I) pyrazolato diimmine complexes. Inorg. Chem. 42, 1248-1255 (2003).
  3. Sudhir Ranjan and S. K. Dikshit. Synthesis, spectroscopic, electrochemical and photophysical behaviour of ruthenium (II) and copper (I) isocyano-bridged complexes with polypyridine ligands: 2,2’-bipyridine and 1,10-phenanthroline. Transition Met. Chem. 27, 668-675 (2002).
  4. Y. Chi, Sudhir Ranjan, T. Y. Chou, C. S. Liu, S. M. Peng, G. H. Lee. Preparation and characterization of the volatile alkaline-earth metal complexes with multiply coordinated aminoalkoxide ligands. J. Chem. Soc., Dalton Trans.  2462-2466 (2001).
  5. Y. Chi, Sudhir Ranjan, P.-W. Chung, C. S. Liu, S. M. Peng, G. H. Lee. Synthesis and characterization of two novel tetra-nuclear sodium ketoiminate complexes: structural evidence for formation of Na…F and Na-C (olefin) bonding interactions. J. Chem. Soc., Dalton Trans. 343-347 (2000).
  6. Sudhir Ranjan and S. K. Dikshit. Synthesis, spectroscopic, photophysical and electrochemical properties of cyano-bridged copper(I)-ruthenium(II) complexes. Polyhedron 17, 3071-3082 (1998)