Indium Selenides: Structural Characteristics, Synthesis and Their Thermoelectric Performances

Abstract

Indium selenides have attracted extensive attention in high-efficiency thermoelectrics for waste heat energy conversion due to their extraordinary and tunable electrical and thermal properties. This Review aims to provide a thorough summary of the structural characteristics (e.g. crystal structures, phase transformations, and structural vacancies) and synthetic methods (e.g. bulk materials, thin films, and nanostructures) of various indium selenides, and then summarize the recent progress on exploring indium selenides as high-efficiency thermoelectric materials. By highlighting challenges and opportunities in the end, this Review intends to shine some light on the possible approaches for thermoelectric performance enhancement of indium selenides, which should open up an opportunity for applying indium selenides in the next-generation thermoelectric devices.

Indium selenide: an insight into electronic band structure and surface excitations

“…Depending on the stacking characteristics, three different polytypes (β, ε, γ) of bulk InSe exist 27, 28 . The β (space group symmetry ) and ɛ (space group symmetry ) polytypes are characterized by a hexagonal lattice consisting of eight atoms in the unit cell and extending over two layers 29 , whereas rhombohedral γ-polytype (space group symmetry ) contains two cations and two anions distributed on four adjacent layers 27, 30 .…”

Thickness-Dependent Dielectric Constant of Few-Layer In2Se3 Nanoflakes

“…In particular, the number of layers (n) in a thin-film 2D system is expected to strongly influence its dielectric constant, a fundamental electrical property that determines the capacitance and charge screening in electronic devices. [4][5][6] The 2D material in this study is the layered semiconducting chalcogenide In2Se3, a technologically important system for phase-change memory, thermoelectric, and photoelectric applications 7 . The In-Se phase diagram is among the most complex ones in binary compounds.…”

“…[8][9][10][11] By controlling the synthesis parameters or thermal/electrical pretreatment processes, several phases (superlattice, simple hexagonal -phase, simple hexagonal -phase, and amorphous state) with vastly different electrical conductivity can coexist at the ambient condition, [12][13][14] which explains the research interest of In2Se3 as a prototypical phasechange material. 7,[12][13][14][15][16][17][18] In addition, the lattice constant of In2Se3 matches well with Bi2Se3, which is heavily investigated for its high thermoelectric figure-of-merit and topological insulator nature. 19,20 The chemical and structural compatibility between the two chalcogenides enables the growth of In2Se3/Bi2Se3 heterostructures.…”

Multi-morphological growth of nano-structured In2Se3 by ambient pressure triethylene glycol based solution syntheses

“…γ-phase In 2 Se 3 is a defect hexagonal wurtzite structure with a band-gap value of 1.8eV, which can be transformed from the former low temperature phases at above 350°C [24].…”

“…Thermodynamically, α-In 2 Se 3 can be formed as both α(3R) and α(2H) crystal structures with bandgap energy of 1.36eV at below 200°C. 8 α(3R)-and α(2H)-In 2 Se 3 have a three layered rhombohedral structure with space group R 3 m and a two layered hexagonal structure with space group P6 3 , respectively [24]. Similar to α-In 2 Se 3 , β-In 2 Se 3 can also crystallize in both β(3R) and β(2H) crystal structures at above 200°C but has different lattice parameters and M A N U S C R I P T…”