To investigate the electron-hole recombination activity of intrinsic point defects in t-Se, we calculate the PES between equilibrium defect geometries for a given charge transition (i.e. charge states q and q ± 1). From these PES and the underlying electronic structure calculations, we compute the nuclear wave function overlaps via the 1D Schrödinger equation and the electron-phonon coupling coefficients via static coupling perturbation theory, which yields the carrier capture coefficients C e/h and cross-sections s e/h . As discussed above, Se vacancies are the only intrinsic point de-|| For Se vacancies the ground-state geometry is the split-chain bipolaron arrangement (Fig. ), but the 'self-healed' type metastable V Se 0* is only slightly higher in energy with a small transition energy barrier (Fig. ). Each plot shows V Se PES in two charge states; X q (and X q with an electron-hole pair of energy equal to the band gap E g ) in blue and X q 1 + h + VBM in orange; along the linear path in structural space between their equilibrium configurations, with the corresponding defect level given as the plot title (q/q 1). The transition from the upper blue (X q + e + h + ) to middle orange (X q 1 + h + ) PES corresponds to electron capture by X q , while that from middle orange to lower blue (X q ) corresponds to hole capture by X q 1 . The x-axis corresponds to the structural/configurational coordinate Q, given in units of mass-weighted displacement (Ångstrom times the square root of the atomic mass unit; amu 0.5 Å). DE h /e denotes the activation energy barrier to hole/electron capture, here for the two cases which show a crossing between PES and thus a classical capture barrier. Filled circles represent calculated energies, and the solid lines are spline fits to the data. A portion of the effective vibrational wave functions are also shown for illustration. "0 ⇤ " indicates the metastable neutral vacancy. In the bottom-right plot, the corresponding charge capture cross-sections of each vacancy defect level are plotted as a function of temperature. The charge of the defect is given by the superscript, and the charge carrier is denoted by the subscript; e/h for electron/hole; s q e/h . For transitions involving the neutral state, the faster of the V Se 0 /V Se 0* rates are shown; which is V Se 0 in all cases except for s 0 e -which is extremely slow in both cases. The charge capture coefficients are plotted in Fig. .