An ideal piezoelectric material for energy harvesting applications have a high piezoelectric coefficient relevant for the mode of operation. The currently realized plastic ionic molecular crystals may not have piezoelectric coefficients that compete with the best commercial metaloxide piezoelectrics, such as PZT and lead magnesium niobate-lead titanate (PMN-PT). Still, the plastic crystals have inherent potential for energy harvesting application due to their low dielectric permittivity. Comparing with commercial inorganics, PZT-5H has a d 33 of 593 pC/N and a relative permittivity of 3400 , while all the plastic crystals studied in this work have dielectric constants below 5. In addition, the plastic crystals have other advantages such as low-temperature synthesis and plasticity in the mesophases which could enable simplified co-fabrication with flexible polymeric substrates used for energy harvesting devices. This process is currently technically challenging for metal oxides, involving etching of sacrificial layers and a process of transfer of the piezoelectric from silicon to polymer substrates . The predicted figures of merits indicate that the quinuclidinium and the dabco compounds have potential for application in shear mode energy harvesting devices. Most energy harvesting devices rely on the longitudinal piezoelectric response, but shear devices have also been studied .