Lead-Free Bi_0.5(Na_0.78K_0.22)TiO₃ Nanoparticle Filler–Elastomeric Composite Films for Paper-Based Flexible Power Generators

Key solutions for material selection, processing, and performance of environmentally friendly high-power generators are addressed. High voltage and high power generation of flexible devices using piezoelectric Bi_0.5(Na_0.78K_0.22)TiO₃ nanoparticle filler–polydimethylsiloxane (PDMS) elastomeric matrix for a lead-free piezoelectric composite film on a cellulose paper substrate is demonstrated. To elucidate the principle of power generation by the piezoelectric composite configuration, the dielectric and piezoelectric characteristics of the composite film are investigated and the results are compared with those of theoretical modeling. The paper-based composite generator produces a large output voltage of ≈100 V and an average current of ≈20 µA (max. ≈30 µA) through tapping stimulation, which is a record-high performance compared to previously reported flexible lead-free piezoelectric composite energy harvesters. Moreover, a triboelectric-hybridized piezoelectric composite device using a micro-patterned PDMS shows a much higher output voltage of ≈250 V and output power of ≈0.5 mW, which drives 300 light-emitting diodes. These results prove that a new class of paper-based and lead-free energy harvesting device provides a strong possibility for enlarging the functionality and the capability of high-power scavengers in flexible and wearable electronics such as sensors and medical devices.