Work

Structural Control of Defect‐Bound Exciton Emission in α‐In 2 Se 3

Year: 2026

Type: article

Abstract: ABSTRACT Native lattice defects strongly govern the optoelectronic properties of ‐, an emerging van der Waals material. At room temperature, its photoluminescence (PL) spectrum features a band‐edge excitonic “A” peak at 1.36 eV and a defect‐related sub‐bandgap “B” peak at 1.3 eV. While the B peak emission brightens significantly below 150 K, its exact origin and its connection to the low‐temperature phase transition of have remained unclear. Here, we demonstrate that the B peak emission originates from excitons trapped at Se vacancies. Upon cooling below 150 K, ‐ undergoes a structural transformation to the phase, which increases the localized electron density at Se vacancies and drives the brightening of the B peak emission. X‐ray photoelectron spectroscopy and a negative Seebeck coefficient confirm the presence of Se vacancies, which introduce electron doping and form a surface two‐dimensional electron gas observed using angle‐resolved photoemission spectroscopy. The trapped excitons exhibit strong electron–phonon coupling, with a PL lifetime of 28 ns and a large Huang–Rhys factor of 14. These results offer a framework for the deterministic control of defect‐bound excitons in ‐ for optoelectronics applications.

Source: Advanced Optical Materials

DOI: 10.1002/adom.71820