SKM 2021 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 23: Focus Session: Highlights of Materials Science and Applied Physics III (joint session DS/HL)
HL 23.5: Vortrag
Freitag, 1. Oktober 2021, 12:15–12:30, H1
Passivating polysilicon recombination junctions for crystalline silicon solar cells — •Franz-Josef Haug1, Audrey Morisset1, Philippe Wyss1, Mario Lehmann1, Aicha Hessler-Wyser1, Andrea Ingenito1, Quentin Jeangros1, Christophe Ballif1, Shyam Kumar2, Santhana Eswara2, and Nathalie Valle2 — 1Ecole Poiytechnique Fédérale de Lausanne (EPFL), School of Engineering, PV-Lab, Switzerland — 2Luxembourg Institute of Science and Technology (LIST), Materials Research and Technology Department, Luxembourg
We investigate polysilicon recombination junctions, whose n-type bottom layer also acts as passivating contact to the silicon surface. They are a key element in tandem devices with a silicon bottom cell, and they could be used to simplify the processing sequence of single-junction cells with interdigitated back contacts. Processing requires high temperatures to crystallize the layers, however, this step can also deteriorate the tunnelling junction by diffusion of dopants. We analyse depth profiles of the doping concentrations in the layers and diffusion across the interface between them by secondary ion mass spectrometry (SIMS) in dynamic mode. We show that undesired diffusion is suppressed by modifying the interface with C, O, or a combination of these. Moreover, we demonstrate that this modification does not interfere with the diffusion of H which is an essential element to passivate defects at the wafer surface. Thus, we find implied open-circuit voltages up to 740 mV for contact resistivities less than 40 mΩcm2, and we demonstrate tandem cells with efficiency above 20%.