Photon conversion efficiency (PCE) as a function of wavelength for NIRSpec in PRISM mode. The shown PCE curve includes the reflectivity of the telescope optics (marked OTE) and the responsive quantum efficiency of the NIRSpec detector array, but excludes the light losses occurring in the slit device employed. The individual contributions making up the total PCE are also shown. The PCE contribution from the detector array exceeds unity at wavelengths below 1.4 μm due to multiple electrons being released for sufficiently energetic photons.