Influence of the roughness (microrelief) of an active interface in p-n junction solar cells (SC) on the photovoltage (the open-circuit voltage V-oc) has been studied. Nonuniformity of contact potential difference between p- and n-regions leads to barrier height fluctuation that are exponentially enhanced when dealing with barrier current. This results in some decrease of the V-oc value. Three theoretical models of averaging open-circuit voltage were used. Experimental results on p(+)-AlxGa1-xAs/p(+)-n-GaAs heterostructure SC with various microrelief, obtained by the anisotropic chemical etching, are compared with theoretical calculations. (c) 2006 Elsevier B.V. All rights reserved.