Organic-silicon Solar Cells Exceeding 20% Efficiency

Abstract Aftera briefreview of therecent evolvement oforganic-silicon heterojunction solar cells,we present here our latest measurements of the saturation current densities ( J 0 ) and contact resistances ( R C ) of crystalline silicon (c-Si)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) junctions. We determine the J 0 values by means of contactless carrier lifetime measurements and the R C values by comparing sheet resistance measurements with numerical device simulations of the corresponding test structure. Application of an adopted PEDOT:PSS blend and an optimized silicon surface treatmentresults in a minimal J 0 value of46 fA/cm 2 , limiting the solar cell open-circuit voltage to V oc_limit =708 mV, and a minimal R C value of 100 mΩcm 2 . Our optimized silicon surface pre-treatment in combination with the adapted PEDOT:PSS blendare successfully implemented into a cell process with the PEDOT:PSS layer located at the rear surface (the so-called ‘BackPEDOT concept’). Record-high efficiencies of 18.3% and of 20.6% are achieved on n -type silicon and on p -type silicon wafers, respectively. Finally, we compare the internal quantum efficiency of our champion BackPEDOT solar cell with that of a state-of-the-art Al 2 O 3 /SiN x -passivated PERC solar cell.