Simulation is essential for a comprehensive analysis of the performance of solar cells. The rear contact pitch of passivated emitter and rear cells (PERC cells) is a crucial device parameter that influences not only the electrical performance but also the optical performance of these cells. This article investigates the applicability of the analytical light trapping model by Basore to account for the optical influence of the rear contact pitch as a simpler alternative to ray tracing. First, we manufacture three different groups of cells with different rear contact pitches, where the metallization fraction f met varies between 0 and 54%. Second, the reflectance of the cells is measured. Subsequently, we fit the model parameters R f and R b (internal reflection on the front and back surface, respectively) to the measured reflectance. While we confirm a nonlinear relation between f met and the measurable spectra found in previous works, our results reveal linear relations between f met and R b with the adjusted coefficients of determination of R adj ² > 0.97, as well as between f met and the charge carrier generation rates with R adj ² > 0.94. These relations allow a simple and rapid optical simulation of f met variation for PERC cells. The same approach is likely applicable to any local contacts also in other cell concepts.

Abstract.As the market share of bifacial cells and modules grows, solar cells measurements under bifacial illumination are increasingly becoming a focus of interest. In this work, we present an analysis of four different sorting criteria for bifacial solar cells with the aim of evaluating the impact of these criteria on the power of the modules assembled with the sorted cells. First, we develop a simulation model for bifacial modules based on the two-diode model. Secondly, we generate a representative virtual data bank made up of 50000 cells, whose parameters are determined in account with empirical parameter distributions measured on a group of 300 bifacial solar cells with passivated emitter and rear (PERC) manufactured industrially. Third, we sort and bin all cells according to the current density under front illumination at maximum power point (MPP) (jmpp . With respect to the average module power, a very small gain of less than 2 W (in the most extreme illumination scenario) can be achieved if a bifacial instead of a monofacial sorting parameter is taken as sorting criterion. However, a strong effect on the distribution of the module power is manifested, obtaining either one homogeneous group of modules with broad power distribution or several classes/bins of modules, depending of the cell sorting criterion. Therefore, the choice of the sorting criteria of the cells depends on the interest of the solar manufacturers and has a great potential to reduce module mismatch in PV arrays.

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