Broadband nonlinear energy harvesting capabilities of a parametrically excited bimorph piezoelectric energy harvester is investigated for the first time. The performance of the energy harvester is significantly enhanced via use of stoppers and an added tip mass in conjunction with parametric excitation. A fully nonlinear electromechanical model of the energy harvester was developed using beam theory of Euler-Bernoulli and the coupled constitutive equations for piezoelectric materials, with the motion constraints modelled as nonlinear springs. A multi-modal discretisation was conducted utilising the Galerkin scheme; the resultant set of equations was examined numerically through use of continuation technique. It is shown that a resonance bandwidth of 46% (normalised with respect to parametric resonance frequency) is achieved which is almost 10 times the resonance bandwidth of the system without any constraints.