Figure 4.

Optoelectronic analysis of FA_1–nCs_nPb(I_1–xBr_x)₃ solar cells with different bandgaps. (a) Sensitive EQE spectra in the bandgap region and calculated bandgap and Urbach energies. (b) Ratio of measured V_oc, J_sc, and FF to their maximum theoretical (radiative) limit (lines are guides to the eye). (c) Relation between the open-circuit voltage in the radiative limit with the electroluminescence quantum efficieny, EQE_EL.of a solar cell (lines) for the four bandgaps studied here. Symbols shows the measured V_oc, allowing the corresponding EQE_EL to be estimated. (d) Electroluminescence (EL) spectra of the same samples recorded over time (up to 10 min) under continuous forward bias. Each cell was driven with a constant current-density equal to the J_sc obtained under simulated solar illumination.