Fig. 1: Solar cell characteristics and parameter comparison.

a,b, Current–voltage characteristics (a) and EQE spectra (b) obtained from in-house measurements as well as externally calibrated and independently certified by Fraunhofer ISE. The inset in a lists the JV (black, certified; red, in-house) and diode parameters as extracted from a one-diode fit to the in-house measurement. The wider voltage range allows for a more accurate determination of the series resistance (R_S). The other diode parameters are the apparent parallel resistance (R_P,app), the dark saturation current density (J₀) and the ideality factor (n). In b the normalized PL and first derivative of the EQE are added, too. c–f, The solar cell parameters FF (c), J_SC (d), V_OC (e) and η (f) of our device as a function of the respective bandgap energy (from dEQE/dE) are compared with literature data (see Table 1 for details). For comparison, the parameters of a state-of-the-art Si heterojunction solar cell (HJT) are added, too³⁷. Different percentages of the theoretical maximum values in the radiative limit as a function of the bandgap are plotted as solid lines. In e, the predicted V_OC trend for an ERE of 1.6%, as measured for the record device presented in this work, is shown by the dashed curve (derived from equation (1)).