Fig. 4: Experimental and modeled EQE spectra of perovskite solar cells with a transparent back contact and a spacer mirror on top.

The simulated EQEs result from two defect functions (Eq. (2)) at photon energies E_d = 0.72 and E_d = 1.09 eV, with σ_d = 0.04 eV, multiplied by |E|² after averaging over the entire perovskite layer, or over a half-normal distribution with a standard deviation of 30 nm, centered at the PTAA–perovskite or at the perovskite–PCBM interface. An Urbach tail has been added to enable comparison with the experimental data. The legend gives the thickness of the MgF₂ optical spacer positioned between the transparent ITO back electrode and the Ag mirror (see Fig. 3c).