Parameterization of the Back-Surface Reflection for PERC Solar Cells Including Variation of Back-Contact Coverage

Abstract

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.

Advanced analysis of internal quantum efficiency measurements using machine learning

“…However, modern solar cells are designed to have a high rear internal reflection to increase the capture of long wavelength light. 24 In these cases, the RF model predicts D B with a high level of accuracy. For example, after removing samples with R B < 0.5 from the test set, the RMSE of D B predictions reduces from 0.0383 to 0.0171.…”

“…This effect is described in Figure 5 below. However, modern solar cells are designed to have a high rear internal reflection to increase the capture of long wavelength light 24 . In these cases, the RF model predicts D B with a high level of accuracy.…”

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“…The increase in J 0 decreases the open-circuit . [3,27,28,39,40] Si 3 N 4 /Si interface Donor type defects at Evþ0.28 eV with concentration 3E11 cm À2 , fixed charge = þ2E12 cm À2 [26] Seff = 27 cm s À1 .…”

“…base width 6 μm and height 4 μm) with 80 nm thick ARC(Si 3 N 4 ). [3,27,28,39,40] SiO 2 /Si interface Acceptor type defects with exponential distribution from 0.4 to 0.5 eV below the conduction band (CB) with peak concentration 1E10 cm À2 , fixed charge = þ1E11 cm À2 [41,42] Seff = 13.4 cm s À1 on rear and 11.2 cm s À1 on front side.…”

“…Front emitter 0.3 μm phosphorus doped with sheet resistance of 90 Ω sq À1 . [27,28,39,40] Al 2 O 3 /Si interface Acceptor type defects at Ec-0.43 eV with concentration 2E11 cm À2 , Fixed charge = À5E12 cm À2 [23][24][25] Seff = 7.2 cm s À1 on rear side.…”