Cesium Lead Halide Perovskite Decorated Polyvinylidene Fluoride Nanofibers for Wearable Piezoelectric Nanogenerator Yarns

Piezoelectric nanogenerators (PENGs) provide a viable
solution
to convert the mechanical energy generated by body movement to electricity.
One-dimensional yarns offer a platform for flexible wearable textile
PENGs, which can conform to body for comfort and efficient energy
harvesting. In this context, we report a flexible piezoelectric yarn,
assembled by one-step cocentric deposition of cesium lead halide perovskite
decorated polyvinylidene fluoride (PVDF) nanofibers, on a stainless-steel
yarn. Perovskite crystals were formed in situ during
electrospinning. Our work demonstrates a nanofiber morphology in which
perovskite crystals spread over the nanofiber, leading to a rough
surface, and complementing piezoelectric nanocomposite formation with
PVDF for superior stress excitation. We investigated how the halide
anions of perovskite affect the piezoelectric performance of PENG
yarns by comparing CsPbBr3 and CsPbI2Br. Effects
of the perovskite concentration, annealing temperature, and deposition
time on the piezoelectric properties of PENG yarns were investigated.
Devices assembled with a single yarn of CsPbI2Br decorated
PVDF nanofibers yield the optimal performance with an output voltage
of 8.3 V and current of 1.91 μA in response to pressing from
an actuator and used to charge capacitors for powering electronics.
After aging in the ambient environment for 3 months, the device maintained
its performance during 19,200 cycles of mechanical stresses. The excellent
and stable electrical performance can be ascribed to the optimized
crystallization of CsPbI2Br crystals, their complementing
performance with PVDF, and formation of nanofibers with uniformity
and strength. The flexibility of piezoelectric yarns enables them
to be bent, twisted, braided, and woven for different textile integrations
while harvesting energy from body movements, demonstrating the potential
for wearable mechanical energy harvesting.