This work presents the results of a detailed series resistance characterization of silicon solar cells with screen-printed front contacts using hotmelt silver paste. Applying the hotmelt technology energy conversion efficiencies up to 18.0% on monocrystalline wafers with a size of 12.5 cut X 12.5 cut have been achieved, an increase of 0.3% absolute compared to cells with conventional screen-printed contacts. This is mainly due to the reduction in the finger resistance to values as low as 14 Omega/m, which reduces the series resistance of the solar cell significantly. To retrieve the lumped series resistance as accurately as possible under the operating condition, different determination methods have been analyzed. Methods under consideration were fitting of the two-diode equation function to a dark IV-curve, integration of the area A under an IV-curve, comparison of a j(sc)-V-oc with a one-sun IV-curve, comparison of the jsc and V-oc points of a shaded curve with the one-sun IV-curve as well as comparison of a dark IV-curve with a one-sun IV-curve, and comparison of IV-curves measured at different light intensities. The performed investigations have shown that the latter four methods all resulted in reliable series resistance values
This article presents a successful laser-powered cofiring process for highly efficient Si solar cells as a more compact and energy-efficient alternative to the conventional firing process in an infrared (IR) lamp-powered heat chamber. The best cell group reaches with laser firing only 0.1% abs lower cell efficiency compared to the best group with conventional firing, demonstrating the industrial potential of this laser firing technology. Adding the laser enhanced contact optimization (LECO) process after firing improves the cell efficiency for laser firing to the level of conventional firing, demonstrating the potential of the combination of the laser firing and the LECO process.
Herein, an inline IR thermography system as an innovative application for real‐time contactless temperature measurement of wafers—both metallized and nonmetallized—during the firing process is successfully realized in an industrial firing furnace as proof of concept and example for a thermography system in a conveyor furnace. As observed by the new system, thermocouples (TCs) seem to measure lower temperature on wafers—especially in combination with TC frames—than wafers exhibit at standard firing conditions (here up to ΔT ≈ 40 K). Furthermore, highly resolved spatial temperature distribution can be successfully measured on the wafer.
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