Seite - 167 - in Photovoltaic Materials and Electronic Devices

measurements according to a θ/2θ configuration. In principle, the XRD spectra indicate that the ZnO films developed without the presence of secondary phases or groups. All thesampleshaveahexagonalwurtzitestructureofZnOandgrewalong thec-axis; thisenabledtheobservationoftheZnO(002)diffractionplaneintheXRD pattern. The increase in intensity of the diffraction peak and also the narrowing of thepeak, inotherwords,decreaseinthefullwidthathalfmaximum(FWHM)ofthe peak, with the length of ZnO NRs increased, and the crystallinity improvement of the ZnO NRs. Existing dye uptake measurements were based on dye desorption from the photoanode after a specified 30 min using a NaOH solution, and the succeeding UV-Vis spectroscopy. For the quantitative analysis of dye loading, the washing course for desorption of dye from the anodes was performed using the known volume of 0.1 mM NaOH aqueous solution. The dye detached from the ZnO NRs as implemented for different lengths of ZnO NRs in literature. Figure 2b illustratestheabsorptionsofsolutionscontaining0.01mMdye, indicatingthatdyes detached from the ZnO NRs at 9- (black line), 18- (red line), and 27-h (blue line), respectively. The area of both films was 1 cm2. The results depicted in Figure 2b can be used to calculate the dye loadings and light absorptions at 530 nm (the peak dye absorption) for the ZnO NRs from the 9-, 18-, and 27-h reactions. The lengths of the 18- and 27-h ZnO NRs were longer than those of the 9-h ZnO NRs, and they demonstrated an improvement in light harvesting and dye loading with increasedNRs. Materials  2015,  8,  page–page  performed  using  the  known  volume  of  0.1  mM  NaOH  aqueous  solution.  The  dye  detached  from  the  ZnO  NRs  as  implemented  for  different  lengths  of  ZnO  NRs  in  literature.  Figure  2b  illustrates  the  absorptions  of  solutions  containing  0.01  mM  dye,  indicating  that  dyes  detached  from  the  ZnO  NRs  at  9‐  (black  line),  18‐  (red  line),  and  27‐h  (blue  line),  respectively.  The  area  of  both  films  was  1  cm2.  The  results  depicted  in  Figure  2b  can  be  used  to  calculate  the  dye  loadings  and  light  absorptions  at  530  nm  ( e  peak  dye  absorption)  for  the  ZnO  NRs  from  the  9‐,  18‐,  and  27‐h  reactions.  The  lengths  of  the  18‐  and  27‐h  Z O  NRs  were  longer  than  those  of  t e  9‐h  ZnO  NRs,  an   they  demonstrated  an  improvement  in  light  harvesting  and  dye  loading  with  increased  NRs.    Figure  2.  (a)  XRD  patterns  of  ZnO  nanorods  grown  with  different  duration;  (b)  Optical  absorption  spectra  of  D‐719  dye  detached  from  the  ZnO  NRs  with  various  lengths.  As  mentioned,  ZnO  NRs  with  various  lengths  were  grown  on  AZO  substrates,  and  these  NRs  were  used  in  DSSCs  (Figure  3).  Figure  3a–f  illustrate  FE‐SEM  images  of  the  respective  ZnO  NRs  from  the  9‐,  18‐,  and  27‐h  reactions  grown  on  the  AZO  substrates,  indicating  that  the  ZnO  NRs  were  adequately  grown  on  substrates  with  a  distinctive,  clear  morphology.  Furthermore,  the  diameters,  lengths,  and  aspect  ratios  of  the  NRs  were  in  the  range  of  76–110  nm,  1.5–5  μm,  and  20.7–47.9,  respectively.  Greene  et  al.  indicated  that  the  growing  temperature  influences  the  upright  growth  of  ZnO  NRs  [16].  Figure 2. (a) XRD patterns of ZnO nanorods grown with different duration; (b) Optical absorption spectra of D-719 dye detached from the ZnO NRs with various lengths. Asmentioned,ZnONRswithvarious lengthsweregrow onAZOsubstrates, and these NRs were used n DSSCs (Figur 3). Figure 3a–f illustrate FE-SEM imagesof therespectiveZnONRsfromthe9-,18-, and27-hreactionsgrownonthe AZOsubstrates, indicatingthat theZnONRswereadequatelygrownonsubstrates with a distinctive, clear morphology. Furthermore, the diameters, lengths, and 167