Stability assessment of a planar perovskite solar cell: Estimating parasitic resistances using a new method

In this study, it is proven that the conventional method of computing the parasitic resistances based on the slope of the tangent line to the J-V curve at short-circuit and open-circuit points can only be accurate enough if the slope of the curve is approximately constant at these points. In most perovskite and dye-sensitized solar cells, the J-V curve has a considerable curvature in the proximity of open-circuit and short-circuit positions. This causes significant errors in computing the parasitic resistances with the conventional method. The slopes of the two oblique asymptotes of the curve are mathematically accurate indicators for the values of parasitic resistances. The facts mentioned above are proven based on theoretical equations and experimental data, and exerting the nonlinear least squares algorithm on the J-V curve data with nearly 0.1 V extension of the voltage range of the curve to values below the short-circuit and above the open-circuit points is proposed for solving this issue. As a case study, a hybrid three-cation two-anion perovskite solar cell with Cs0.05(MA0.17FA0.83)0.95Pb (I0.83Br0.17)3 as the absorber layer and CIS as the hole transport layer is fabricated and the J-V characteristic of the cell is used to validate the method. The photovoltaic parameters and the J-V curve recorded immediately after fabrication were compared with those of the same cell after two months to assess the stability and the changes in the values of the parasitic resistances. This method is additionally verified by SCAPS 1-D simulations for both undegraded and degraded solar cells.