Seite - 125 - in Photovoltaic Materials and Electronic Devices

In contrast, Figure 10 shows an increased impact of Rscr with cell length, as in thiscase, the longercell length increases thecurrentdensity,but theTCOmetal contactarea(busbaronly)remains thesame. Forall cellswithametallic interconnect, thecellswithametallicgridshowahighercell efficiency(Figure11)comparedto thecellswithonlyaTCOasthe frontcontact forsimilarRscr (Figure10). 2.5. Influenceof IlluminationPower Solarpanelsandsolarcellsare testedandcertifiedatan illuminationpowerof 1000 W/m2 (also denoted as onesun). Therefore, the panelconfiguration is usually optimized for this high intensity. However, in northwest Europe, this high power is seldom reached. In real life, much of the power generated by solar panels is actually around an illumination power of 500 W/m2. For cells without a metallic grid, the influenceof the illuminationpowerwasinvestigatedwithvariationof thecell length, as shown in Figure 12a. Seemingly, as the illumination power decreases, the impact of the cell length drops. However, when these data are normalized, as shown in Figure 12b, it is seen that the relative power is merely shifted toward somewhat highercell lengthsandthe impact is reducedfor longercells. Nevertheless,down to an illumination power of 0.5 suns, the cell length remains a critical part of the configurationoptimization. Materials  2016,  9,  96  the  relative  power  is  merely  shifted  toward  somewhat  higher  cell  lengths  and  the  impact  is  reduced  for  longer  cells.  Nevertheless,  down  to  an  illumination  power  of  0.5  suns,  the  ell  length  remains  a  critical  part  of  the  configuration  optimization.  Figure  12.  Efficiency  as  function  of  the  cell  length  for  different  light  intensities  (see  legend  in  sun  units,  whereby  one  sun  is  1000  W/m2):  (a)  calculated  values;  (b)  normalized  values.  For  cells  with  a  finger  grid,  the  cell  efficiency  seems  to  become  less  affected  by  the  cell  length,    as  shown  in  Figure  13,  which  shows  efficiency  as  function  of  the  cell  length  for  illumination  powers  from  0.2  to  1  sun  in  Figure  13a–d.  Note  that  for  each  graph,  the  minimum  value  on  the  x‐axis  is  about  half  of  the  maximum  value  to  facilitate  comparison  with  Figure  12b.    Figure 12. Efficiency as function of the cell length for different light intensities (see legend in sun units, whereby one sun is 1000 W/m2): (a) calculated values; (b) normalizedvalues. For cells with finger grid, the cell efficiency seems to become less affected bythecell length,asshowninFigure13,whichshowsefficiencyas functionof the cell lengthfor illuminationpowers from0.2 to1suninFigure13a–d. Note that for each graph, the minimum value on the x-axis is about half of the maximum value to facilitatecomparisonwithFigure12b. 125