Molecular Polarizability Regulated Piezoelectricity of Organic Materials from Single-Molecular Level

Although molecular piezoelectric materials are ideal constituents for next-generation electronic microdevices, their weak piezoelectric coefficients which restrict their practical applications need to be enhanced by some strategies. Herein, a series of d-phenylalanine derivatives are synthesized and an increased molecular piezoelectric coefficient of their assemblies is achieved by acid doping. The acid doping can increase the asymmetric distribution of charges in the molecules and in turn molecular polarizability, leading to the enhanced molecular piezoelectricity of assemblies. The effective piezoelectric coefficients can be promoted up to 38.5 pm V^-1 and four times those without doping, which is also higher than those obtained by the reported methods. Moreover, the piezoelectric energy harvesters can generate voltage up to 3.4 V and current up to 80 nA. This practical strategy can enhance piezoelectric coefficients without varying the crystal structures of the assemblies, which may inspire future molecular design of organic functional materials.