Halide (Cl/Br)-Incorporated Organic–Inorganic Metal Trihalide Perovskite Films: Study and Investigation of Dielectric Properties and Mechanical Energy Harvesting Performance

Compositional tuning of organic–inorganic metal trihalide perovskites (OTPs) via halide (Cl/Br) incorporation has attracted increased attention due to the rapid advancements in the performance of optoelectronic devices based on mixed halide perovskites. It is expected that the fine-tuning of OTPs can significantly enhance the dielectric and piezoelectric properties that are beneficial for constructing a high-performance piezoelectric nanogenerator (PENG). However, few studies on these aspects have so far been reported. In the present study, mixed halide perovskite thin films with various halide (Cl or Br) contents were fabricated by a simple two-step spin-coating method. The effects of fine-tuning the halide composition of methylammonium lead iodide perovskite (MAPbI3) on the morphological, electrical, dielectric, and piezoelectric properties of the perovskite thin films were systematically investigated. In addition, the feasibility of using these mixed halide-MAPbI3 thin films in mechanical energy-harvesting systems was also thoroughly examined by constructing a series of flexible PENGs. The energy-harvesting performance of the PENG was found to be significantly influenced by the amount of incorporated Cl or Br in the MAPbI3 film. Among all the fabricated PENGs, the 4Cl-MAPbI3 PENG poled at 50 kV/cm exhibited a much higher piezoelectric output performance, with an output voltage of ∼5.9 V and an output current density of ∼0.61 μA/cm2. Thus, the present study demonstrates a simple and reliable method for tuning the dielectric and piezoelectric properties of the OTP materials toward developing flexible, high-performance devices which may offer a wide range of utility in wearable and portable electronic devices.