Fig. 7
From: Room temperature multi-phonon upconversion photoluminescence in monolayer semiconductor WS2
Temperature dependence of upconverted emission with the energy gain of 37 meV. a Schematic representation of the experiment: typical PL spectra with indicated by red arrows excitation energies used in UPC measurements at corresponding temperatures. b–f Examples of normal (green line) and upconversion (red line) photoluminescence spectra (green and red lines, respectively) recorded at 20 K, 80 K, 100 K, 120 K, 140 K, respectively. g The normal (green circles) and upconverted (red circles) excitonic photoluminescence integrated intensities as a function of temperature
