Published online by Cambridge University Press: 16 February 2011
We have measured electroabsorption (EA) in a-Si:H p-i-n solar cells in order to estimate their built-in potentials V bi . This Method was pioneered by the Osaka University group; in simple cases V bi is identified with a parameter V 0 obtained by a simple linear fit to the dependence of EA on external bias voltage. Using signal averaging techniques we are able to Measure V 0 with a reproducibility of better than 2%. In one sample from the Institute of Energy Conversion with an a-SiC:H p + layer we estimate V bj = 0.97 ± 0.06 V, which is in good agreement with previous JVT Measurement. The reason that the error estimate is larger than the reproducibility error is the presence of several small effects not accounted for by the original EA theory: in particular V 0 depends slightly on the laser wavelength. We attribute these effects to the small portion of V bi dropped in the a-SiC:Hp + layer, which has a different electroabsorption than a-Si:H. We discuss models for the wavelength dependence.