Visible White-Light Emission and Carrier Dynamics Observed in Full-Series GaSe1-xSx (0≤x≤1) Multilayers

Near-band-edge emissions ranging from red (& AP;630 to 602 nm) to green (& AP;550 to 534 nm) and blue (& AP;494 to 480 nm) colors have been detected in full-series GaSe1-xSx (0 & LE;x & LE;1) multilayers using micro-photoluminescence (& mu;PL) measurements from 4 to 300 K. The multilayered chalcogenides crystallize in a hexagonal structure, with observed mixed stacking phases of & epsilon; and & beta; polymorphs through X-ray diffraction and Raman measurements. The & mu;PL results, along with experimental band-edge characterization through thermoreflectance, identify the & epsilon;-stacked phase as the crucial phase responsible for direct recombination and the emission of free excitons within the visible range. A mixed-color white light is created by PL, which is emitted from the layered GaSe1-xSx series of different colors, and is positioned at the center of the CIE coordination plot (i.e., white color). To assess the emission properties of both band edges and defects in the layered compounds, time-resolved photoluminescence (TRPL) is employed, using an area mapping function. The photoluminescence decay lifetime increases as the sulfur content is increased, owing to the greater occurrence of mixed-phase stacking faults near the & beta;-GaS end within the GaSe1-xSx (0 & LE;x & LE;1) series. The multilayer GaSe1-xSx (0 & LE;x & LE;1) represents a distinct 2D chalcogenide series well-suited for emitting full-color visible light.