Page - 183 - in Photovoltaic Materials and Electronic Devices

monochromator, (Cornerstone 260, Newport, Irvine, CA, USA). The light that exits the monochromator (λexc = 430 nm) is focused on to the colloidal solution. The second one is an IR laser module of 780 nm. Both down- and up-conversion are detected using a second monochromator (Cornerstone 260, Newport, Irvine, CA, USA), positioned at a 90˝ angle to the first monochromator. The monochromator is scanned over the visible wavelength region and the fluorescence signal is detected bythephotomultiplier tube(PMT77340,Newport, Irvine,CA,USA), locatedat the exit port of the second monochromator. Then, the visible fluorescent emission is monitoredusingapowermeter (2935C,Newport, Irvine,CA,USA). Transmission electron microscope (TEM) (JEOL 1400, Peabody, MA, USA), is used to image the synthesized REDC NPs. The mean diameter of the nanoparticles is calculated using ImageJ software through Gaussian distribution of many size measurements. The operating parameters of the XRD (PANalytical X’Pert PRO, Amestrdam, The Netherlands), are 45 KV, 40 A and Cu Kα radiation (λ=0.15406nm). The conductivity of the solution of the synthesized nanoparticles ismeasuredbyA500Orionmeter (Thermoscientific,TechPark,Singapore). 7  The  optical  absorption  is  measured  using  a  dual‐beam  UV‐Vis‐NIR  spectrometer  (UV‐3101PC  Shimadzu,  Tokyo,  Japan).  After  the  annealing  procedure,  a  solution  of  nanoparticles  is  prepared  with  a  concentration  of  0.02  mg  of  nanoparticles  in  10  mL  of  DI  water.  The  colloidal  solution  is  illuminated  with  both  near‐UV  and  near  infra‐red  (NIR)  excitations  in  an  experimental  apparatus  that  was  designed  to  measure  the  down‐  and  up‐conversion  process,  as  described  in  Figure  8.  The  fluorescence  spectroscopy  system  consists  of  two  excitation  sources.  The  first  one,  the  near  UV  excitation,  is  a  Xenon  lamp  coupled  to  a  monochro ator,  (Cornerstone  260,  Newport,  Irvine,  CA,  USA).  The  light  that  exits  the  monochromator  (λexc  =  430  nm)  is  focused  on  to  the  colloidal  solution.  The  second  one  is  an  IR  laser  module  of  780  nm.  Both  down‐  and  up‐conversion  are  detected  using  a  second  monochromator  (Cornerstone  260,  Newport,  Irvine,  CA,  USA),  positioned  at  a  90°  angle  to  the  first  monochromator.  The  monochromator  is  scanned  over  the  visible  wavelength  region  and  the  fluorescence  signal  is  detected  by  the  photomultiplier  tube  (PMT  77340,  Newport,  Irvine,  CA,  USA),  located  at  the  exit  port  of  the  second  monochromator.  Then,  the  visible  fluorescent  emission  is  monitored  using  a  power  meter  (2935C,  Newport,  Irvine,  CA,  USA).  Transmission  electron  microscope  (TEM)  (JEOL  1400,  Peabody,  MA,  USA),  is  used  to  image  the  synthesized  REDC  NPs.  The  mean  diameter  of  the  nanoparticles  is  calculated  using  ImageJ  software  through  Gaussian  distribution  of  many  size  measurements.  The  operating  parameters  of  the  XRD  (PANalytical  X’Pert  PRO,  Amestrdam,  The  Netherlands),  are  45  KV,  40  A  and    Cu  Kα  radiation  (λ  =  0.15406  nm).  The  conductivity  of  the  solution  of  the  synthesized  nanoparticles  is  measured  by  A500  Orion  meter  (Thermo  scientific,  Tech  Park,  Singapore).    Figure  8.  Up‐  and  down‐conversion  fluorescence  setup.  3.3.  Coating  Procedure  The  synthesized  nanoparticles  are  coated  on  the  back  sides  of  polycrystalline  solar  cells    (2  inches  ×  2  inches)  ordered  from  Solar  Winds  Inc.,  Austin,  TX,  USA.  Coating  has  been  operated  Figure8. Up-anddown-conversionfluorescencesetup. 3.3. CoatingProcedure The synthesized nanoparticles are c ated on the back sides of pol crystalline solar cells (2 inchesˆ 2 inches) ordered from Solar Winds Inc., Austin, TX, USA. Coating has been operated using spin coater at 1500 rpm for a minute. Before coating, the electrodes on the backside of the cell have been covered through a scotch and released after the coating. That could avoid the direct contact between the nanoparticles and the metallic electrodes. The surface profile is detected using 3D optical surface profiler ZeGage (Zygo, Middlefield, CT, USA), with concentrating on the edge between coated cell and non-coated electrode to detect the thickness. 183