This paper presents an initiative concept in geometry and material lay-up toward energy conversion enhancement of piezoelectric energy harvesters from wideband excitation signals. The energy harvester demonstrated in this work has Macro-fiber-composite (MFC) as active layers and composite laminate as the center shim. This concept utilizes variable cross-sectional area and rotating fiber orientation in the MFC active layer. The simulation of the energy harvester is carried out using finite element (FE) method with high-order shear elements. Results of the FE mode is validated with experimental data and numerical results from COMSOL®. Effects of changing the cross-section, rotation of fibers in the substrate and the active piezoelectric layers on output power and natural frequency of the harvester are analyzed. The results point out the optimum piezoelectric fiber orientation, at which power and power density are, respectively, 20% and 60% higher compared to zero-fiber angle. In addition, taper angle, as a key parameter in shifting the harvester natural frequency, can be used for broadband energy harvesters. By a combination of the taper angle and optimum fiber orientation, a broadband energy harvester was optimally designed for a moving car. Power generation by the designed harvester is 84% greater than a common multi-beam design at a 47%-reduced volume resulting a 160% power density improvement.