Abstract Worldwide energy crisis and environmental pollution issues are driving people to seek for clean energy harvesting technologies as alternative and/or complementary energy sources for traditional fossil fuel, in which piezoelectric nanogenerators are extensively studied for mechanical energy harvesting due to their high energy density, simple architectures and excellent scaling-down capacity. Poly(vinylidene fluoride) (PVDF) and its copolymer with trifluoroethylene (P(VDF-TrFE)) are mostly studied piezoelectric polymers. Recent work indicated that the largest longitudinal coefficient occurred at the morphotropic phase boundary of P(VDF-TrFE) with 50 mol.% VDF content (CVDF), while P(VDF-TrFE) with higher CVDF was mostly studied. Thus it is indispensable to further understand the influence of CVDF on piezoelectric performance in order to optimize the design of P(VDF-TrFE) based sensors and energy harvesters in various practical applications. Here we made a systematic investigation of the dependence of longitudinal and transverse piezoelectric properties on CVDF in commercially available 50/50, 55/45 and 70/30 copolymers. Experimental results indicated that 50/50 copolymer presented the largest longitudinal piezoelectric property and thus provided the best electric response for tactile sensing while 70/30 one showed the most outstanding transverse piezoelectricity and applied for monitoring the bending of fingers. In energy harvesting experiments at maximum strain of 1.2% and frequency of 0.6 Hz, 70/30 copolymer showed the largest power density of 4.96 nW/mm2, while 55/45 copolymer had the highest energy conversion efficiency of 1.03%. Device performance was expected to be further improved by controlling film quality and microstructures.

中文翻译：

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传感和能量收集应用中压电 P(VDF-TrFE) 薄膜的 VDF 含量引导选择

摘要 世界范围的能源危机和环境污染问题促使人们寻求清洁能源收集技术作为传统化石燃料的替代和/或补充能源，其中压电纳米发电机由于其高能量密度、简单架构和出色的缩减容量。聚偏二氟乙烯 (PVDF) 及其与三氟乙烯的共聚物 (P(VDF-TrFE)) 是研究最多的压电聚合物。最近的工作表明，最大的纵向系数出现在具有 50 mol.% VDF 含量 (CVDF) 的 P(VDF-TrFE) 的同向相界处，而主要研究的是具有较高 CVDF 的 P(VDF-TrFE)。因此，为了在各种实际应用中优化基于 P(VDF-TrFE) 的传感器和能量收集器的设计，进一步了解 CVDF 对压电性能的影响是必不可少的。在这里，我们对市售的 50/50、55/45 和 70/30 共聚物中纵向和横向压电特性对 CVDF 的依赖性进行了系统研究。实验结果表明，50/50 共聚物表现出最大的纵向压电性能，从而为触觉传感提供最佳电响应，而 70/30 共聚物表现出最出色的横向压电性能，可用于监测手指弯曲。在最大应变为 1.2% 和频率为 0.6 Hz 的能量收集实验中，70/30 共聚物的最大功率密度为 4.96 nW/mm2，而55/45共聚物的能量转换效率最高，为1.03%。通过控制薄膜质量和微观结构，预计器件性能将得到进一步提高。