Ever since two dimensional-transition (2D) metal dichalcogenides (TMDs) were discovered, their fascinating electronic properties have attracted a great deal of attention for harnessing them as critical components in novel electronic devices. 2D-TMDs endowed with an atomically thin structure, dangling bond-free nature, electrostatic integrity, and tunable wide band gaps enable low power consumption, low leakage, ambipolar transport, high mobility, superconductivity, robustness against short channel effects and tunneling in highly scaled devices. However, the progress of 2D-TMDs has been hampered by severe charge transport issues arising from undesired phenomena occurring at the surfaces and interfaces. Therefore, this review provides three distinct engineering strategies embodied with distinct innovative approaches to optimize both carrier injection and transport. First, contact engineering involves 2D-metal contacts and tunneling interlayers to overcome metal-induced interface states and the Fermi level pinning effect caused by low vacancy energy formation. Second, dielectric engineering covers high-k dielectrics, ionic liquids or 2D-insulators to screen scattering centers caused by carrier traps, imperfections and rough substrates, to finely tune the Fermi level across the band gap, and to provide dangling bond-free media. Third, material engineering focuses on charge transfer via substitutional, chemical and plasma doping to precisely modulate the carrier concentration and to passivate defects while preserving material integrity. Finally, we provide an outlook of the conceptual and technical achievements in 2D-TMDs to give a prospective view of the future development of highly scaled nanoelectronic devices.

Flexible electronics are expected to play a key role in connecting human lives with versatile smart electronic devices due to their adaptability to different shapes, surfaces, and even the human body. However, heat management issues found in most flexible devices due to the low thermal conductivity of conventional plastic or paper substrates become significant for large-scale integration or high-temperature applications. In this study, we employed high thermal conductivity nanopaper composed of two-dimensional (2D) hexagonal boron nitride nanosheets and one-dimensional nanofibrillated cellulose to form a flexible deep-ultraviolet photodetector demonstrating superior photodetectivity of up to 8.05 × 10¹⁰ cm Hz^1/2/W, a short response time of 0.267 s, and excellent flexible durability featuring repeatable ON/OFF photoswitching over 200 bending cycles. Because the boron nitride paper has a high thermal conductivity of 146 W/mK, which is three orders of magnitude larger than plastic or paper substrates, the photodetectors can work at high temperatures of up to 200 °C. The boron nitride paper-based strategy described herein suggests a path for improving heat dissipation in flexible electronics and achieving high-performance deep-ultraviolet photodetectors, which can be applied in wearable applications.

Single crystal metal‐free halide perovskites have received great attention in recent years owing to their excellent piezoelectric and ferroelectric properties. However, the nanotoxicity and piezoelectricity within the nanoscale of such materials have yet been reported for the demonstration of practical applications. In this work, the observation of intrinsic piezoelectricity in metal‐free perovskite (MDABCO‐NH₄I₃) films using piezoresponse force microscopy (PFM) is reported. A cytotoxicity test is also performed on MDABCO‐NH₄I₃ to evaluate its low‐toxic nature. The as‐synthesized MDABCO‐NH₄I₃ is further integrated into a piezoelectric nanogenerator (PENG). The MDABCO‐NH₄I₃‐based PENG (MN‐PENG) exhibits optimal output voltage and current of 15.9 V and 54.5 nA, respectively. In addition, the MN‐PENG can serve as a self‐powered strain sensor for human–machine interface applications or be adopted in in vitro electrical stimulation devices. This work demonstrates a path of perovskite‐based PENG with high performance, low toxicity, and multifunctionality for future advanced wearable sensors and portable therapeutic systems.

Metal‐halide perovskites have emerged as versatile materials for various electronic and optoelectronic devices such as diodes, solar cells, photodetectors, and sensors due to their interesting properties of high absorption coefficient in the visible regime, tunable bandgap, and high power conversion efficiency. Recently, metal‐free organic perovskites have also emerged as a particular class of perovskites materials for piezoelectric applications. This broadens the chemical variety of perovskite structures with good mechanical adaptability, light‐weight, and low‐cost processability. Despite these achievements, the fundamental understanding of the underlying phenomenon of piezoelectricity in metal‐free perovskites is still lacking. Therefore, this perspective emphasizes the overview of piezoelectric properties of metal‐halide, metal‐free perovskites, and their recent progress which may encourage material designs to enhance their applicability towards practical applications. Finally, challenges and outlooks of piezoelectric metal‐free perovskites are highlighted for their future developments.