Passivated emitter and rear cell (PERC) solar cells are currently being introduced into mass production. In this paper, we report a novel PERC solar cell design that applies a screen-printed rear Al finger grid instead of the conventional full-area aluminum (Al) rear layer while using the same PERC manufacturing sequence. We name this novel cell concept PERC+ because it offers several advantages. In particular, the Al paste consumption of the PERC+ cells is drastically reduced to 0.15 g instead of 1.6 g for the conventional PERC cells. The Al fingers create 2-μm-deeper aluminum back surface fields, which increases the open-circuit voltage by 4 mV. The five-busbar Al finger grid enables bifacial applications of the PERC+ cells with front-side efficiencies up to 20.8% and rear-side efficiencies up to 16.5% measured with a black chuck. The corresponding bifaciality is 79%. When applied in monofacial modules where the white back sheet acts as external rear reflector, the efficiency of the PERC+ cells is estimated to 20.9%, which is comparable with conventional PERC cells. Whereas Institute for Solar Energy Research Hamelin developed the aforementioned PERC+ results, SolarWorld independently pioneered a very similar bifacial PERC+ cell process starting in 2014. Transfer into mass production has been successfully accomplished, and novel glass-glass bifacial PERC+ modules have been launched at the Intersolar 2015 based on a most simple, lean, and cost-effective bifacial cell process. These new bifacial PERC+ modules show an increase in annual energy yield between 5% and 25% in simulations, which is confirmed by first outdoor measurements.
We present a holistic approach for the photovoltaic (PV) module frame improvement that considers mechanical, electrical, economic, and ecological aspects for different frame designs. In a comprehensive study, the approach is applied to exemplary PV module frame designs. The analyses performed in this study show a potential improvement path of the module frame design. This leads to an overall better module performance and helps finding the balance point between technical performance, cost, and environmental impact. Based on the results, the PV module frame design affects the aspects analyzed in this work differently. For the comparison, we defined reference frame design with 16 and 20 mm front and rear frame widths. The improvement is reached by unitizing the frame width for both sides to 18 mm and increasing its cavity width to 12 mm instead of 8.5 mm. Tuning the frame parameters in this way leads to the best balance point for frame designs in this study regarding all aspects. The mechanical finite element method (FEM) simulation results show that
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