PVDF based flexible piezoelectric nanogenerators using conjugated polymer:PCBM blend systems

Piezoelectric energy harvesting technology has received much attention as a powerful source of energy for a self-powered system. In this study, three main conjugated polymers that have delocalized π-electrons and excellent charge transport properties were studied: poly(3-hexylthiophene) (P1), poly[(4,8-di-(2-ethylhexyloxy)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl)-alt-(5,5′-yl-4,4′-bis(dodecyl)-2,2′-bithiophene)] (P2) and poly[(4,8-di-(2-ethylhexyloxy)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl)-alt-(5,5′-yl-4,4′-bis(2-ethylhexyl)-2,2′-bithiophene)] (P3). Each of three polymers was blended with phenyl-C61-butyric acid methyl ester (PCBM61), and the blend systems were used to make PVDF based piezoelectric nanogenerators (PNG-0-3). Polymers showed bimodal structures that have a majority edge-on orientation, forming a minority face-on orientation. At a 2 Hz frequency and 0.2 mm displacement, the output voltages (peak-to-peak) of PNG-(0-3) were 35.0 V, 41.2 V, 42.2 V and 43.1 V, respectively, and the output currents (peak-to-peak) were 558.5 nA, 569.5 nA, 572 nA and 589 nA, respectively. The energy conversion efficiencies of PNGs (0-3) were 6.47%, 11.62%, 13.36%, and 14.33%, respectively; therefore, the efficiency was improved by up to about 2.2 times.