(A) Contour plot of the PL spectra of device D1 as a function of photon energy (bottom axis) and n₀ (left axis). The out-of-plane electric field F_z is fixed at zero. (B) PL spectra at diverse n₀. Cyan and green peaks represent Lorentz-fit peaks for RMX_1&2 and RMT_1&2, respectively. Note that the range of 1.45–1.60 eV in both (A) and (B) are magnified by 10 times for clarity. Offset is set in (B) for better resolution. (C) Lorentz-fitted results extracted from (B) of X_A (red hollows), X_A^- (carmine hollows), RMX₁ (green triangles), RMX₂ (blue cubes), RMT₁ (light green triangles) and RMT₂ (light blue cubes). The binding energy of X_A^-, RMT₁ and RMT₂ is approximately 24, 59 and 57 meV, respectively.