Perovskite nanostructures and heterostructures represent a rapidly advancing field in semiconductor research, driven by their exceptional optoelectronic properties and tunable characteristics at the nanoscale. Low-dimensional perovskite systems, such as nanowires and nanoplatelets, exhibit quantum confinement effects, enhanced light-matter interactions, and improved charge transport compared to their bulk counterparts. When integrated into heterostructures with oxides or two-dimensional materials, these systems enable precise control over interfacial phenomena, strain engineering, and carrier dynamics, opening new possibilities for next-generation devices.

Nanowires and nanoplatelets are among the most studied perovskite nanostructures due to their anisotropic geometries and high surface-to-volume ratios. Perovskite nanowires, typically synthesized via solution-based methods or vapor-phase deposition, demonstrate strong carrier confinement along the radial direction while maintaining efficient longitudinal transport. For instance, methylammonium lead iodide (MAPbI3) nanowires exhibit reduced defect densities compared to thin films, leading to enhanced photoluminescence quantum yields exceeding 60%. Nanoplatelets, with thicknesses confined to a few unit cells, show thickness-dependent bandgap tuning, with shifts as large as 0.5 eV observed when reducing the thickness from 10 to 3 layers. These systems also exhibit suppressed electron-phonon coupling, resulting in narrow emission linewidths below 20 meV, making them attractive for light-emitting applications.

Strain engineering plays a critical role in modulating the properties of perovskite nanostructures. Lattice mismatch at interfaces or external stress application induces strain, which can alter band structures, carrier mobilities, and stability. Compressive strain in CsPbBr3 nanoplatelets has been shown to increase the bandgap by up to 150 meV, while tensile strain reduces it by a similar magnitude. Strain can also influence exciton binding energies, with reports indicating a 30% increase under compressive strain due to enhanced electron-hole overlap. In nanowires, axial strain gradients can create built-in electric fields that facilitate charge separation, improving photovoltaic performance. However, excessive strain can lead to phase segregation or degradation, requiring careful optimization during growth and integration.

Heterostructures combining perovskites with oxides or 2D materials offer additional degrees of freedom for property tailoring. Perovskite/oxide interfaces, such as LaAlO3/SrTiO3 with perovskite quantum wells, exhibit two-dimensional electron gases with mobilities exceeding 10,000 cm²/Vs at low temperatures. The high dielectric constant of oxides like TiO2 or Al2O3 can screen Coulomb interactions, reducing exciton binding energies in adjacent perovskite layers from 50 meV to below 20 meV. Charge transfer at these interfaces is strongly influenced by band alignment, with type-II heterojunctions facilitating efficient electron-hole separation. For example, in CsPbBr3/Bi2O3 systems, ultrafast charge transfer occurs within 200 fs, as evidenced by transient absorption spectroscopy.

Perovskite/2D material heterostructures leverage the atomically smooth surfaces and dangling-bond-free interfaces of graphene or transition metal dichalcogenides. MoS2/MAPbI3 stacks demonstrate photoinduced hole transfer from the perovskite to the MoS2 layer with efficiencies above 80%, while graphene electrodes in contact with perovskite nanoplatelets enable transparent contacts with sheet resistances below 100 Ω/sq. Hexagonal boron nitride (hBN) serves as an ideal encapsulation layer, improving perovskite stability against moisture by a factor of 10 while maintaining photoluminescence intensity over weeks. Van der Waals assembly allows strain-free integration, avoiding lattice mismatch issues common in epitaxial systems.

Carrier confinement in perovskite nanostructures is governed by both quantum size effects and dielectric contrast. In nanoplatelets thinner than the exciton Bohr radius (approximately 5 nm for MAPbI3), quantization energies follow a 1/d² dependence, where d is the thickness. Dielectric confinement further enhances exciton binding energies, reaching values up to 300 meV in 3-layer CsPbBr3 systems. Nanowires exhibit radial confinement, with diameter-dependent absorption edges shifting by over 0.3 eV when reducing diameters from 50 nm to 10 nm. This strong confinement enables population inversion at lower thresholds, with amplified spontaneous emission observed at carrier densities as low as 10¹⁷ cm⁻³.

Interfacial charge transfer dynamics in heterostructures are critical for device performance. Time-resolved studies reveal that electron transfer from perovskite to TiO2 occurs within 100 fs, while hole transfer to spiro-OMeTAD happens on picosecond timescales. In 2D hybrid systems, interlayer excitons form at the interface with lifetimes extending into the nanosecond range, compared to sub-nanosecond bulk exciton lifetimes. The charge transfer rates depend strongly on interface quality, with trap-assisted recombination reducing efficiencies at defective interfaces. Surface passivation using organic ligands or atomic layer deposition can improve transfer yields by passivating surface states.

Thermal and environmental stability remain challenges for perovskite nanostructures. Encapsulation strategies using Al2O3 or polymer matrices can extend operational lifetimes from hours to months under ambient conditions. Thermal conductivity in nanowires is anisotropic, with values along the wire axis measuring 1.5 W/mK, significantly higher than the 0.3 W/mK observed in thin films. This directional heat dissipation helps mitigate thermal degradation during high-power operation.

The versatility of perovskite nanostructures and heterostructures continues to drive innovations across optoelectronics, photonics, and quantum technologies. Their compatibility with solution processing and room-temperature synthesis makes them particularly attractive for scalable manufacturing. Future developments will likely focus on improving interface control, understanding degradation mechanisms, and integrating these materials into complex device architectures. The ability to precisely engineer strain, confinement, and charge transfer at the nanoscale positions perovskite-based systems as key enablers for advanced functional devices beyond the limitations of conventional semiconductors.