26.1%-efficient POLO-IBC cells

Quantification of electrical and optical loss mechanisms

authored by: Christina Hollemann, Felix Haase, Sören Schäfer, Jan Krügener, Rolf Brendel, Robby Peibst
Abstract: We present experimental results for interdigitated back contacted (IBC) solar cells with passivating POLO contacts for both polarities with a nominal intrinsic poly-Si region between them. We reach efficiencies of 26.1% and 24.9% on a 1.3 Ω cm and 80 Ω cm p-type FZ wafer and 24.6% on a 2 Ω cm n-type Cz wafer, respectively. The initially measured implied efficiency potentials of the cells after passivating the surfaces are very similar, namely, 26.8%, 26.8%, and 26.4%, respectively. We attribute the difference between the efficiency potential and the final current-voltage measurement to degradation, perimeter, and series and shunt resistance losses, which we quantify by lifetime measurements. With these measurements in combination with a finite element simulation, we determine the surface recombination velocity in the nominal intrinsic poly-Si region to be in the range from 13 to 21 cm s⁻¹. Using the same approach, we analyze the increase of the front surface recombination velocity during cell processing from 2 to 10 cm s⁻¹ for the 1.3 Ω cm and from 0.5 to 2.3 cm s⁻¹ for the 80 Ω cm. This leads to the fact that cells fabricated on lowly doped bulk material are more vulnerable to a process-induced degradation of the surface passivation quality. We further determine the theoretical limits of the cells by firstly idealizing the recombination (28% for 1.3 Ω cm and 28.2% for 80 Ω cm) and secondly also idealizing the optics of the solar cells (29.4% and 29.5%).
Organisation(s): Institute of Electronic Materials and Devices
Laboratory of Nano and Quantum Engineering
Solar Energy Section
External Organisation(s): Institute for Solar Energy Research (ISFH)
Type: Article
Journal: Progress in Photovoltaics: Research and Applications
Volume: 27
Pages: 950-958
No. of pages: 9
ISSN: 1062-7995
Publication date: 01.11.2019
Publication status: Published
Peer reviewed: Yes
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Renewable Energy, Sustainability and the Environment, Condensed Matter Physics, Electrical and Electronic Engineering
Sustainable Development Goals: SDG 7 - Affordable and Clean Energy
Electronic version(s): https://doi.org/10.1002/pip.3098 (Access: Closed)