This paper is concerned with a geometrically nonlinear solid shell element to analyze piezoelectric structures. The finite element formulation is based on a variational principle of the Hu-Washizu type and includes six independent fields: displacements, electric potential, strains, electric field, mechanical stresses and dielectric displacements. The element has 8 nodes with 4 nodal degrees of freedoms, 3 displacements and the electric potential. A bilinear distribution through the thickness of the independent electric field is assumed to fulfill the electric charge conservation law in bending dominated situations exactly. The presented finite shell element is able to model arbitrary curved shell structures and incorporates a 3D-material law. A geometrically nonlinear theory allows large deformations and includes stability problems. Linear and nonlinear numerical examples demonstrate the ability of the proposed model to analyze piezoelectric devices.