PERC+: industrial PERC solar cells with rear Al grid enabling bifaciality and reduced Al paste consumption

• Published in: Progress in photovoltaics Vol. 24; no. 12; pp. 1487 - 1498
• Main Authors: Dullweber, Thorsten, Kranz, Christopher, Peibst, Robby, Baumann, Ulrike, Hannebauer, Helge, Fülle, Alexander, Steckemetz, Stefan, Weber, Torsten, Kutzer, Martin, Müller, Matthias, Fischer, Gerd, Palinginis, Phedon, Neuhaus, Holger
• Format: Journal Article
• Language: English
• Published: Bognor Regis Blackwell Publishing Ltd 01.12.2016; Wiley Subscription Services, Inc
• Subjects: Al finger grid; Aluminum; bifacial; Consumption; Efficiency; Fingers; five busbars; Modules; Pastes; PERC; Photovoltaic cells; rear passivation; screen printing; Solar cells
• ISSN: 1062-7995; 1099-159X
• DOI: 10.1002/pip.2712

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. Copyright © 2015 John Wiley & Sons, Ltd. Whereas conventional industrial PERC solar cells apply a full‐area Al layer at the rear, in this paper, we introduce a novel PERC solar cell design that applies a screen‐printed Al finger grid while using the same PERC manufacturing sequence. We name this novel cell concept PERC+ because it offers several advantages compared with conventional PERC cells such as a strongly reduced Al paste consumption, a deeper aluminum back surface field, and enabling of bifacial applications. First performance data of industrially manufactured bifacial PERC+ modules are presented as well.