Fabrication of piezoelectric polymer multilayers on flexible substrates for energy harvesting

Piezoelectric polymer materials typically possess overly high electrical impedances for energy harvesting applications, which can be reduced by the implementation of multilayer configurations to achieve improved impedance matching with electrical loads and thus significantly increased energy utility. An efficient and reliable method to produce piezoelectric polymer multilayer structures suitable for energy harvesting is in great demand. Here, piezoelectric P(VDF-TrFE) polymer multilayers were fabricated on a flexible substrate by alternately dip coating P(VDF-TrFE) layers and evaporating thin film aluminum electrodes. Appropriate methods and conditions were established to overcome major processing challenges, including redissolving of previous layers by the solvent in the coating solution in the multiple-cycle solution coating process. The internal thin film electrodes were dedicatedly designed and processed to directly form reliable electrical connections without etching the P(VDF-TrFE) layers or applying extra inactive adhesive layers. With a fabricated piezoelectric cantilever comprising ten layers of P(VDF-TrFE) polymer on a flexible aluminum substrate, the experimentally obtained voltage and energy output at a tip deflection of 7 mm reached 6.7 V and 16.8 μJ respectively, with a load of 30 kΩ. As multiple devices over a large area could be produced with the dip coating process, the fabrication method as demonstrated is scalable for batch manufacture.