High‐eficiency silicon solar cells: Si/SiO₂, interface parameters and their impact on device performance

Abstract

Abstract This article presents the first measurements of the parameters of the Si/SiO 2 , interfaces employed on the record‐efficiency silicon solar cells made at the University of New South Wales (UNSW). the UNSW oxides are characterized by very low values of the surface state density (∼4 × 10 −9 cm −−2 eV‐ −−1 ), low values for the positive fixed oxide charge density (∼7 × 10 −10 cm −−2 ) and a pronounced asymmetry in the capture cross‐sections of electrons and holes. Using the microwave‐detected photoconductance decay method, we verify experimentally that these oxide parameters produce a strong dependence of the effective surface recombination velocity at oxidized p‐type silicon surfaces on the excess electron concentration within the wafer. In high‐performance silicon solar cells, this phenomenon produces a long‐wavelength spectral response that strongly depends on the bias light intensity, a characteristic ‘hump’ in the dark current‐voltage characteristics and fill factors that are lower than would be expected from the high open‐circuit voltages of 700 mV.