X-RAY PHOTOELECTRON SPECTROSCOPY (XPS) STUDY OF THE PRINTED-SIO_x DL CAPIN PERC-TYPE SOLAR CELL APPLICATION

摘要

In our previous work, we demonstrated that an efficiency gain of 0.13% can be achieved by implementing a dual capping (DL CAP, SiO_x/SiN_x) layer on our unique printed-AlO_x passivated emitter and rear cells (PERC) technology. The SiO_x layer was deposited by using screen printing and was confirmed to be a composite of Si02 and Si (OH)_x by using Fourier-transform infrared spectroscopy (FT-IR) analysis. The Si (OH)_x was speculated to be an oxidizing-agent provider which decomposes during firing, and then the released oxidizing agents diffuse to and oxidize the AlO_x/Si interface as a result of the reduction in the interface trap density (D_(it)) and better passivation quality In this work, we further analyzed the elemental composition and the electronic state of the elements of DL CAP and baseline (BSL) by using X-ray photoelectron spectroscopy (XPS) depth profile analysis. XPS result confirmed that DL CAP has a higher degree of oxidation than BSL do at the AlO_x/Si interface (O atomic %: 24.3 in DL CAP vs. 18.1 in BSL). Moreover, the binding energy of 0 Is is about 534.1 eV in the printed SiO_x layer and shifts towards lower bonding energy of 532.7 eV as approaching the AIO_x/Si interface, meaning transformation from hydroxide to oxide as approaching the AIO_x/Si interface. These XPS results are consistent with the FT-IR results and are as the supporting evidence for the passivation mechanism we speculated.