Herstellung und Untersuchung von beidseitig passivierten kristallinen Siliziumsolarzellen

Solar cells are an alternative and environmental friendly energy source to convert solar energy into electrical energy. The high silicon consumption is so far limiting a faster growth of the solar industry. The reduction of the wafer thickness is not easy to establish, since the thickness reduction will also result in an efficiency reduction, if processed conventionally. The aim of this thesis is to develop a concept for the industrial processing of double side passivated solar cells with high efficiencies on thin silicon substrates. For this reason the potential of silicon nitride (a-SixNy:Hz) for surface passivation was investigated by measuring the minority carrier lifetime. Especially the layer composition was observed and in detail characterized by Fourier transformed infrared spectroscopy (FTIR). The investigated silicon nitride layers were deposited in a plasma enhanced chemical vapor deposition (PECVD) batch reactor. With a plasma generation frequency of 440 kHz surface recombination velocities below 70 cm/s on 1 omega cm float zone silicon (FZ-Si) and below 30 cm/s on 6 omega cm Czochralski silicon were obtained. This demonstrates that even with a low frequency plasma a reasonable surface passivation for double side passivated silicon solar cells by a-SixNy:Hz layer can be achieved. The FTIR bond analysis reveals a fundamental difference between very silicon rich a-SixNy:Hz layers (refractive index n greater than or equal to 2.2) in terms of high temperature process steps compared to stoichiometric and weak silicon rich a-SixNy:Hz layers. Furthermore the contact formation of aluminum and silicon with an a-SixNy:Hz layer in between was investigated and optimized. The surface morphology was identified as a crucial factor and has a decisive influence on the contact quality. Based on these investigations a new solar cell process was developed, which combines the benefits of a double side passivated solar cell (higher efficiency at lower wafer thickness) with the requirements of industrial mass production. This new process yields higher efficiencies of delta eta = 0.5% on multi-crystalline silicon in comparison to a conventional aluminum back surface field (BSF) process. Complementary simulations with PC1D were carried as well as optimizing as defining the limits of this new process. Thereby it was found that nearly no back surface field is formed and the base doping is limiting the open circuit voltage. This newly developed process is compatible with multi-crystalline as well as mono-crystalline silicon and offers a large field of application. Besides the utilization in standard modules, where the higher front side efficiency is beneficial, new module designs like for building integrated photovoltaic or semi transparent modules are feasible.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2009

Author dc:creator

• Janßen, Lars

Contributors dc:contributor

• Kurz, Heinrich

• info:eu-repo/classification/ddc/620
• Solarzelle
• Passivierung
• PECVD-Verfahren
• Ingenieurwissenschaften
• Siliziumnitrid
• solar cell
• silicon nitride
• passivation
• PECVD

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-113315%22

OAI record oai:identifier

https://publications.rwth-aachen.de/oai2d?verb=GetRecord&metadataPrefix=oai_dc&identifier=oai%3Apublications.rwth-aachen.de%3A50788