Modeling the edge effect for measuring the performance of mesoscopic solar cells with shading masks

Perovskite solar cells (PSCs) have attracted intensive attention in the past several years due to their ever-increasing efficiency. Particularly, high efficiencies are usually obtained by small-area (0.1 cm(2)) lab cells, and thus, the cell performance can be easily over- or underestimated due to inappropriate measurement protocols. Shading masks with well-defined apertures are usually employed to determine the test area of the cells. However, it is found that the aperture area significantly influences the measured photovoltaic parameters of the cells, and has not been quantified. Here we measure and compare the parameters of printable mesoscopic PSCs with shading masks of different shapes and aperture areas. It is identified that extra diffuse light may go through the masks due to the edge effect, and cause an overestimation of the photocurrent density (J(SC)). We establish a model to calibrate the measured J(SC), which is considered as a sum of effective J(SC) (J(SC-eff)) and error J(SC) (J(SC-err)). By fitting the J(SC) measured using apertures of 0.031-0.503 cm(2) with a quadratic function, J(SC-eff) and J(SC-err) are respectively obtained. Besides the aperture areas, the ratio of aperture area/active area also influences the open-circuit voltage and fill factor of the cells. By fitting the measured values with different apertures, we establish a model to calibrate the measured parameters of PSCs. This model can evaluate the test errors and provide effective values of the photovoltaic parameters of PSCs.