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Tracking	  the	  Adsorp2on	  and	  Electron	  Injec2on	      Rates	  of	  CdSe	  Quantum	  Dots	  on	  TiO2:	  	         L...
Big	  Picture	  •  Quantum	  dot	  sensiHzed	  solar	  cells	  (QDSSCs)	  are	  cheap	   	   	       	      	   	  devices...
Goal	  1:	  Understand	  QD	  AdsorpHon	              Phenomenon	  on	  TiO2	  Experimental	  setup	  for	  monitoring	  C...
AdsorpHon	  Processes	  QDs	  begin	  to	  form	  a	  monolayer	  on	  TiO2	  before	  aggregaHng	  on	  the	  TiO2	  surf...
AdsorpHon	  Modeling	                                0.06          Experimental Adsorption Data                           ...
Effect	  of	  Washing	  on	  QD	  AdsorpHon	                                           25     QD Adsorbed Per TiO2 Nanopart...
Goal	  2:	  Examine	  Charge	  Carrier	  Dynamics	  for	                    QD-­‐TiO2	  Assemblies	  	                    ...
Electron	  InjecHon	  Rates	                           "#$%&!($)*                   +,-     +,.         +,/          0,1  ...
Summary	  •  Development	  of	  a	  method	  to	  monitor	  and	  model	  QD	  adsorpHon	     onto	  TiO2	  over	  Hme	  •...
Special	  Thanks	                    –	  U.S.	  Department	  of	  Energy	  for	  project	  funding	   –	  Vincent	  P.	  S...
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Adsorption and Electron Injection for CdSe on TiO2


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This presentation is based on the recent publication from our group entitled, "Tracking the Adsorption and Electron Injection Rates of CdSe Quantum Dots on TiO2: Linked versus Direct Attachment," published in 2011 in the Journal of Physical Chemistry C. Presented by Doug Pernik, an undergraduate in the Kamat lab.

Figures in this presentation are reprinted with permission from J. Phys. Chem. C, 2011, 115, 13511-13519. Copyright 2011 American Chemical Society.

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Adsorption and Electron Injection for CdSe on TiO2

  1. 1. Tracking  the  Adsorp2on  and  Electron  Injec2on   Rates  of  CdSe  Quantum  Dots  on  TiO2:     Linked  versus  Direct  ADachment   Douglas  R.  Pernik,  Kevin  Tvrdy,  James  G.  Radich,  Prashant  V.  Kamat   J.  Phys.  Chem.  C,  2011,  115  (27),  pp  13511-­‐13519   Department  of  Chemical  and  Biomolecular  Engineering   Department  of  Chemistry  and  Biochemistry   RadiaHon  Laboratory,  University  of  Notre  Dame  
  2. 2. Big  Picture  •  Quantum  dot  sensiHzed  solar  cells  (QDSSCs)  are  cheap            devices  for  converHng  solar  energy  to  electricity  •  Current  QDSSCs  lack  in  efficiency  compared  to  crystalline            silicon    •  Improvements  are  needed  at  the  QDSSC  working  electrode  Goals  of  this  work:      –  Understand  quantum  dot  adsorpHon  phenomenon  on  TiO2    –  Examine  charge  carrier  dynamics  for  QD-­‐TiO2  assemblies  
  3. 3. Goal  1:  Understand  QD  AdsorpHon   Phenomenon  on  TiO2  Experimental  setup  for  monitoring  CdSe  QD  adsorpHon  on  TiO2.    AdsorpHon  is  seen  over  Hme  with  UV-­‐Visible  absorpHon  spectrometry.  
  4. 4. AdsorpHon  Processes  QDs  begin  to  form  a  monolayer  on  TiO2  before  aggregaHng  on  the  TiO2  surface  
  5. 5. AdsorpHon  Modeling   0.06 Experimental Adsorption Data Sub-Monolayer Adsorption QD AggregationFractional Coverage of TiO2 0.05 Total Fit 0.04 0.03 0.02 0.01 0.00 0 10 20 30 40 50 Time (Hours) AdsorpHon  is  seen  as  a  combinaHon  of  monolayer   formaHon  and  QD  aggregaHon  on  TiO2  
  6. 6. Effect  of  Washing  on  QD  AdsorpHon   25 QD Adsorbed Per TiO2 Nanoparticle 5 Washes 20 15 3 Washes 10 5 1 Wash 0 0 10 20 30 40 50 Time (Hours) Methanol  pretreatment  (washing)  improves  QD  affinity  for  TiO2  
  7. 7. Goal  2:  Examine  Charge  Carrier  Dynamics  for   QD-­‐TiO2  Assemblies     Flow of Electrons Electron Electrolyte Light Transfer QD TiO2 Photoanode Photocathode How  does  the  presence  of  a  molecular  linker  affect  electron  injecHon  rates?  
  8. 8. Electron  InjecHon  Rates   "#$%&!($)* +,- +,. +,/ 0,1 !D! (3D3I* !"#$%&()$"%*+%#,-./,-<=>, ∆<=>,?/,0 0 !"#$%&()*+,-),./01$)$ !D! (=D=I* !"#$%"0$1*&2%3**314$"%*+%#,-./,- 5$67+($(*3&%5$8*9:* ! !!!!!!!!!!! |∆<=>@%=3#A$B!(#@%8,!83C?0* ()9 ∆<?/,//+ (89 3 #-234!"#$%&()*+ = ! 3I ()9∆<=>@%=3#A$ ∆<?/,//+ (89 .-234!"#$%&()*+ =I ()9 ∆<?/,//+ (89 #-23456#4!"#$%&()*+ ! ()9 ∆<?/,//- (89 .-2345674!"#$%&()*+ / 9-/ -// --/ :// :-/ ;// / +/ 9/ :/ 1/ 0// 234$5$#&67!(#8* E$53!FG8$!(H>* Electron  injecHon  is  more  rapid  when  QDs  are  directly  adsorbed  onto  TiO2.     The  linker  molecule  3-­‐MPA  acts  as  a  physical  barrier  to  charge  transfer  
  9. 9. Summary  •  Development  of  a  method  to  monitor  and  model  QD  adsorpHon   onto  TiO2  over  Hme  •  Importance  of  QD  washing  to  achieve  high  coverage  of  TiO2  •  AdsorpHon  is  seen  as  a  combinaHon  of  monolayer  formaHon  and   parHcle  aggregaHon  •  Linker  molecules  have  a  detrimental  effect  on  electron  injecHon   rates   These  findings  will  aid  in  construcHng  quantum  dot  sensiHzed  solar   cells  with  higher  efficiency  
  10. 10. Special  Thanks   –  U.S.  Department  of  Energy  for  project  funding   –  Vincent  P.  Slac  Fellowship  for  Undergraduate  Research,  provided  by   Notre  Dame  Energy  Center   This  work  is  published  in  the  Journal  of  Physical  Chemistry  C:   J.  Phys.  Chem.  C,  2011,  115  (27),  pp  13511-­‐13519   DOI:  10.1021/jp203055d  AddiHonal  informaHon  about  the  Kamat  group  is  on  the  group  website:     hcp://