A Comprehensive Review on Piezoelectric Polymeric and Ceramic Nanogenerators

Piezoelectric nanogenerators (PNGs) have recently received significant attention because of their great potential for harvesting electricity from wasted mechanical energy resources. In spite of many studies on piezoelectric energy harvesters, a comprehensive review that summarizes alternative types of piezoelectric materials is yet to be reported. This article categorizes piezoelectric materials into two types: piezoelectric perovskite and wurtzite micro‐/nanostructures ceramics and ferroelectric polymers and compares their energy harvesting capabilities and piezoelectric properties. Piezoelectric inorganic materials with a perovskite structure, such as lead magnesium niobate−lead titanate (PMN−PT, d 33 = 2500 pCN −1 ) and lead zirconate titanate, d 33 = 500–600 pCN −1 ) PNGs, generate the highest output voltage and current density among all piezoelectric materials. However, the piezoelectric coefficient d 31 (−28 to ≈−69 pC N −1 ) of PMN−PT is lower than PZT (−175 pC N −1 ) and its toxicity and expensive fabrication process have limited its utilization. Cellular polypropylene (PP) as a ferroelectret polymer offers a high piezoelectric coefficient d 33 (250−1400 pC N −1 ), although their d 31 is lower than piezoelectric poly(vinylidene fluoride) (PVDF) polymer. Piezoelectric natural polymers such as cellulose ( d 33 ≈ 8−28 pC/N, silk ( d 33 ≈ 0.3−0.8 pC/N, and collagen ( d 33 ≈ 22 pC/N are also introduced for bio‐PNG applications to tackle environmental problems. There is still a research gap on rationally designed self‐powered, wearable, stretchable, and biocompatible PNGs with high and controllable energy conversion efficiency.