EU PVSEC Programme Online
EU PVSEC 2021, 6 - 10 September 2021
Presentation: 2CO.15.3 Impact of the Bulk Resistivity and Operation Temperature on Silicon Solar Cells
Type: Oral
Date: Wednesday, 9th September 2020
17:00 - 18:30
Author(s): A. Augusto, A. Srinivasa, A.H.T. Le, J.P. Seif, Z. Hameiri, S.G. Bowden
Presenter / Speaker: A. Augusto, Arizona State University, Tempe, USA
Event: Conference Conference
Session: 2CO.15 Measurement and Analysis of Crystalline Silicon Solar Cells
Type(s) of Access:  Conference Registration
Topic: 2. 5 Characterisation & Simulation of Si Cells
Summary / Abstract: Today's highest-efficiency solar cells typically operate near the threshold between low and high injection. It is not well understood whether pushing the cell operation point further into a high injection regime throughout the day is beneficial for the solar cell performance. In this study we present a comprehensive assessment, both experimental and by simulation, of how bulk resistivity, defects and operation temperature impact the performance of the solar cell. Analytical simulations indicate that high bulk resistivity wafers (10 Ωcm to >15 kΩcm) require bulk Shockley-Read-Hall lifetimes in the millisecond range to outperform wafers with standard bulk resistivities (<10 Ωcm). Additionally, for bulk resistivities beyond 10 Ωcm, the cell efficiency is shown to be weakly dependent of bulk resistivity. This study is particularly relevant today, as solar cell architectures with better surface passivation and milliseconds lifetimes wafers are commercially available, leveraging potential benefits of using higher bulk resistivities. Previous studies on high bulk resistivities are limited, inconclusive and lacked experimental data above 100 Ωcm. In this work, we fabricate amorphous/crystalline silicon heterostructures and silicon heterojunction solar cells on n-type substrates with bulk resistivities from 1Ω.cm to >15 kΩcm. We measure their performance at different operation temperatures between 30 oC and 80 oC. The temperature coefficients are calculated from implied voltages at open circuit and maximum power, and from implied fill factors as a function of temperature. They are shown to be independent of the bulk resistivity and exhibit similar values as previously reported on standard bulk resistivities wafers. The surface saturation current density increases by several orders of magnitude for all bulk resistivities and show a cubic dependence of temperature. This temperature dependence was previously reported on standard bulk resistivities wafers. The significant increase of the surface saturation current density with temperature can be partially explained with a similar increase of the effective intrinsic carrier concentration. We are currently finalizing silicon heterojunction solar cells over a large range of bulk resistivities, the conclusions of which will be reported at the conference.