Piezoelectricity of organic polymers has attracted increasing interest because of several advantages they exhibit over traditional inorganic ceramics. While most organic piezoelectrics rely on the presence of intrinsic local dipoles, a highly nonlocal electronic polarisation can be foreseen in conjugated polymers, characterised by delocalised and highly responsive π-electrons. These 1D systems represent a physical realisation of a Thouless pump, a mechanism of adiabatic charge transport of a topological nature which results, as shown in this work, in anomalously large dynamical effective charges, inversely proportional to the bandgap energy. A structural (ferroelectric) phase transition further contributes to an enhancement of the piezoelectric response reminiscent of that observed in piezoelectric perovskites close to morphotropic phase boundaries. First-principles density functional theory (DFT) calculations performed in two representative conjugated polymers using hybrid functionals, show that state-of-the-art organic piezoelectric are outperformed by piezoelectric conjugated polymers, mostly thanks to strongly anomalous effective charges of carbon, larger than 5e—ordinary values being of the order of 1e—and reaching the giant value of 30e for band gaps of the order of 1 eV.

有机聚合物的压电由于与传统无机陶瓷相比具有多种优势而引起了越来越多的关注。虽然大多数有机压电材料依赖于固有局域偶极子的存在，但在共轭聚合物中可以预见高度非局域电子极化，其特征是离域和高度响应的π电子。这些一维系统代表了无量泵的物理实现，无量泵是一种拓扑性质的绝热电荷传输机制，如本工作所示，它会导致异常大的动态有效电荷，与带隙能量成反比。结构（铁电）相变进一步有助于增强压电响应，让人想起在接近同形相边界的压电钙钛矿中观察到的响应。使用混合泛函在两种代表性共轭聚合物中进行的第一性原理密度泛函理论 (DFT) 计算表明，最先进的有机压电材料的性能优于压电共轭聚合物，这主要归功于碳的强反常有效电荷，大于5 e - 普通值约为 1 e -对于 1 eV 量级的带隙，达到 30 e的巨大值。