Halide perovskite-based mechanical energy harvester for self-powered sensing

• Main Author: Jiang, Feng
• Other Authors: Lee Pooi See
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2025
• Subjects: Engineering; Materials
• Online Access: https://hdl.handle.net/10356/181932
• Institution: Nanyang Technological University

The rapid advancement of wearable electronics has intensified the demand for efficient power supply and intelligent sensing systems. Mechanical energy harvesters, such as triboelectric nanogenerators (TENGs) and tribovoltaic nanogenerators (TVNGs), offer effective means by converting mechanical energy from the environment and human movements into electricity. This provides a sustainable and self-powered solution for driving multifunctional electronic devices and sensing systems. Among various materials, halide perovskites show their exceptional electrical performance, owing to their tunable energy levels and remarkable ferroelectricity. However, the comprehensive understanding of halide perovskite interfaces, including charge transfer behaviors and interfacial bonding interactions, remains elusive. This gap necessitates deeper investigation to establish theoretical frameworks and propose potential optimization strategies for fabricating high-performance energy harvesters and sensors. Furthermore, the usage of lead and the moisture sensitivity of halide perovskites make them suffer from high toxicity and poor stability, impeding their further practical applications. Therefore, the aim of this thesis is to develop high-efficiency mechanical energy harvesters and self-powered sensors based on lead-free halide perovskites, while delving into the charge transfer behaviors of various perovskite-involved interfaces. To achieve this goal, three different interfacial systems, including perovskite/polymer interface based on van der Waals force, perovskite/metal interface based on Schottky junction, as well as perovskite/elastomer interface based on supramolecular interaction, have been designed. In the first project, lead-free Cs3Bi2Br9 perovskites were adopted to construct a stable perovskite/polymer van der Waals interface through a co-electrospinning of Cs3Bi2Br9 /poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and styrene–ethylene–butylene–styrene (SEBS). PVDF-HFP would create a nanofiber network and Cs3Bi2Br9 would be embedded into the nanofibers during the electrospinning process, while SEBS formed microspheres that mechanically interlock the nanofibers, endowing the composite with excellent stretchability. In this work, Cs3Bi2Br9 functions as charge trapping fillers and nucleating agents that enhance the surface charge accumulation and polar crystalline proportion of the PVDF-HFP. After the perovskite content optimization, a high output power density (2.34 W m-2) could be achieved, which was ten times higher than the pure composite without perovskites. In addition to the van der Waals interaction, the perovskite/metal interface was also investigated to understand the charge transfer behaviors at the Schottky junction. A copper-based (3,3-difluorocyclobutylammonium)2CuCl4 [(DF-CBA)2CuCl4] perovskite with multiaxial ferroelectricity has been designed to construct an aluminum/(DF-CBA)2CuCl4 Schottky junction TVNG. Owing to the excellent ferroelectric polarization, the surface charge and work function of (DF-CBA)2CuCl4 can be effectively controlled through the electrical poling process, resulting in a strong built-in electric field and large space charge layer at the interface. After the optimization of the electric poling field, a 15-fold current output regulation can be achieved, offering a new strategy for high-performance direct-current nanogenerator design. To further improve the interfacial interaction, a stretchable and self-healable porous elastomer poly(siloxane-diphenylglyoxime-urethane (PSDU) has been synthesized, which can form diverse hydrogen bonds with (DF-CBA)2CuCl4. The incorporation of (DF-CBA)2CuCl4 not only improves the charge trapping capacity but also promotes the charge transfer process and mechanical properties of the composite, attributing to the strong hydrogen bonding interactions between elastomer and (DF-CBA)2CuCl4. As a result, the power output of porous PSDU-perovskite composite (1.87 W m-2) was ten times higher than pure porous PSDU (0.14 W m-2) and over three orders of magnitude greater than dense PSDU-based TENG (1.28 mW m-2). In summary, this study investigated the optimization strategies and working mechanisms of halide perovskite-based mechanical energy harvesters and self-powered sensors, focusing on material design and interfacial charge transfer mechanisms, which offer promising avenues for the self-powered perovskite-based energy devices.