A simple method for pinhole detection in carrier selective POLO-junctions for high efficiency silicon solar cells

authored by: D. Tetzlaff, J. Krügener, Y. Larionova, S. Reiter, M. Turcu, F. Haase, R. Brendel, R. Peibst, U. Höhne, J. D. Kähler, T. F. Wietler
Abstract: Polycrystalline silicon (poly-Si) layers on thin silicon oxide films have received strong research interest as they form excellent carrier selective junctions on crystalline silicon substrates after appropriate thermal processing. Recently, we presented a new method to determine the pinhole density in interfacial oxide films of poly-Si on oxide (POLO)-junctions with excellent electrical properties. The concept of magnification of nanometer-size pinholes in the interfacial oxide by selective etching of the underlying crystalline silicon is used to investigate the influence of annealing temperature on pinhole densities. Eventually, the pinholes are detected by optical microscopy and scanning electron microscopy. We present results on the pinhole density in POLO-junctions with J₀ values as low as 1.4 fA/cm². The stability of this method is demonstrated by proving that no new holes are introduced to the oxide during the etching procedure for a wide range of etching times. Finally, we show the applicability to multiple oxide types and thickness values, differently doped poly-Si layers as well as several types of wafer surface morphologies. For wet chemically grown oxides, we verified the existence of pinholes with an areal density of 2×10⁷ cm⁻² even already after annealing at a temperature of 750 °C (lower than the optimum annealing temperature for these junctions).
Organisation(s): Institute of Electronic Materials and Devices
Institute of Solid State Physics
Laboratory of Nano and Quantum Engineering
External Organisation(s): Institute for Solar Energy Research (ISFH)
Centrotherm International AG
Type: Article
Journal: Solar Energy Materials and Solar Cells
Volume: 173
Pages: 106-110
No. of pages: 5
ISSN: 0927-0248
Publication date: 12.2017
Publication status: Published
Peer reviewed: Yes
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Renewable Energy, Sustainability and the Environment, Surfaces, Coatings and Films
Sustainable Development Goals: SDG 7 - Affordable and Clean Energy
Electronic version(s): https://doi.org/10.1016/j.solmat.2017.05.041 (Access: Closed)