Doping of poly-Si contacts for high efficiency back junction back contact silicon solar cells using inkjet-printed doping sources
Final Report Abstract
The aim of the project was to investigate different printable doping sources for the doping of POLy-Si on Oxide (POLO) passivating contact for c-Si solar cells. The motivation for this was to find a low-cost way to fabricate high efficiency back-junction back-contacted (BJBC) solar cells. Typically, the fabrication of BJBC solar cells involves complicated process sequences, especially for the local doping of the electron and hole contacting regions, with printable doping sources having the potential to simplify the process significantly. So far, doping from printable doping sources has been associated with low charge carrier lifetimes, most likely caused by low material purity leading to diffusion of recombination active elements, like Fe or Cu into the Si wafer. This low lifetime makes the use of these sources unsuitable for backjunction solar cells, or other high efficiency Si solar cells. Since POLO contacts have been shown to getter impurities from Si wafers, applying less pure materials on POLO contacts could be much less detrimental. Thus, the combination of printable doping sources and POLO contacts could enable a lean process flow for BJBC solar cells, without impacting the solar cell efficiency. During the first half of the project, a poly-Si baseline for furnace diffused POLO contacts has been established at UNSW. Further a process optimisation for doping via spin-on dopants has been conducted, as well as first successful inkjet printing experiments. During a visit to Germany, high performing undoped POLO precursors have been provided by the project partners at ISFH and doped Si NP inks have been deposited on test samples by the project partners at UDE. After this promising start of the project, further progress was hindered by an extensive lab remediation project at SPREE, resulting in the closure of different labs vital for this project. During this period of lab closures, different side projects that did not require these labs have been pursued. The most exciting one resulted in the fabrication of a prototype of an optrode array for biomedical application. A future application of such a device could be the local stimulation of nervous tissue for a brain machine interface. By replacing electrical wires with optical fibres these devices could become much smaller and safer. While not everything worked out as planned, the DFG research fellowship provided me with an amazing opportunity to conduct my own research in a high-class research environment. It enabled me to strengthen my network with PV researchers in Australia and internationally.
Publications
- “Plasma Oxidation for Polycrystalline Silicon-Based Passivated Contact”, 2DV.1.72, EU PVSEC 2019, Marseille, France, 2019
Lee C.-Y., Deng S., Zhang T., Khoo K., Romer U., Hoex B.
- “Towards bi-directional electro-optic neuronal interfaces”, Biophotonics Australasia; Melbourne, Australia, 2019
Wang H., Römer U., Lei X., Wei Y., Abed A.A., Ladouceur F., Silvestri L., Lovell N.
(See online at https://doi.org/10.1117/12.2539997) - “Characterizing Point Contacting by Localized Dielectric Breakdown and Its Use in Silicon Solar Cell Applications”, IEEE Journal of Photovoltaics, 2020;10(1):78-84
Ye Q., Western N.J., Römer U., Bremner S.P.
(See online at https://doi.org/10.1109/JPHOTOV.2019.2953394)
