The electronic band structure of indium selenide: photoemission and theory

Hot Carrier and Surface Recombination Dynamics in Layered InSe Crystals

Layered indium selenide (InSe) is a van der Waals solid that has emerged as a promising material for high-performance ultrathin solar cells. The optoelectronic parameters that are critical to photoconversion efficiencies, such as hot carrier lifetime and surface recombination velocity, are however largely unexplored in InSe. Here, these key photophysical properties of layered InSe are measured with femtosecond transient reflection spectroscopy. The hot carrier cooling process is found to occur through phonon scattering. The surface recombination velocity and ambipolar diffusion coefficient are extracted from fits to the pump energy-dependent transient reflection kinetics using a free carrier diffusion model. The extracted surface recombination velocity is approximately an order of magnitude larger than that for methylammonium lead-iodide perovskites, suggesting that surface recombination is a principal source of photocarrier loss in InSe. The extracted ambipolar diffusion coefficient is consistent with previously reported values of InSe carrier mobility.

Structural modification and band-gap crossover in indium selenide nanosheets

Herein, we report on the synthesis of InSe nanosheets.

The Spectroscopy of InSe Nanoparticles

The synthesis of several different sizes of InSe nanoparticles from organometallic precursors is reported. These particles are characterized by transmission electron microscopy, electron diffraction, and optical spectroscopy. The electron diffraction results and optical properties indicate that these particles are two-dimensional disks, consisting of single Se-In-In-Se tetralayer sheets. The absorption spectra indicate strong quantum confinement along the z axis and, for the smaller particles, in the x,y plane. The z-axis quantum confinement may be quantitatively understood in terms of the band structure of bulk InSe. The results indicate that the z-axis quantum confinement reverses the order of the direct and indirect transitions in the case of the largest particles. The smaller particles exhibit strong, polarized fluorescence, and the fluorescence polarization may also be understood in terms of the band structure of bulk InSe.