A method is presented to extract solar cell parameters from the derivatives of dark current–voltage curves with a three-diode model, using the monotonic properties of the current–voltage characteristic associated with each diode or resistive current. The method yields an improved accuracy of the solar cell parameters when compared with that used on the actual current–voltage curves. Despite the complexity of the three-diode model with seven fit parameters, a good accuracy can be reached using the proposed method with a relatively small computational effort. A hypothetical case is presented using various approaches to obtain the solar cell parameters, with a root-mean-square error for the logarithm of the current–voltage curve ( $\text{RMS}_{\text{log}_{10}I}$ ) of $4{\,\,\times\, 10}^{-3}$ . An example fitting is then demonstrated on a multicrystalline passivated emitter rear contact solar cell, yielding $\text{RMS}_{\text{log}_{10}I}=1.45{\,\,\times\, 10}^{-1}$ .