Title :
Formation of a back contact by fire-through process of screen-printed silicon solar cells
Author :
Sopori, Bhushan ; Mehta, Vishal ; Guhabiswas, Debraj ; Reedy, Robert ; Moutinho, Helio ; To, Bobby ; Shaikh, Aziz ; Rangappan, A.
Author_Institution :
Nat. Renewable Energy Lab., Golden, CO, USA
Abstract :
We have investigated various mechanisms that participate in formation of a good, screen-printed, Si-Al contact on the back side of a crystalline-Si solar cell. We observed a rapid diffusion of Si into Al during the temperature ramp-up. The Si diffusion produces a graded composition that causes an Al-Si melt to initiate from the interface. The interface melt of eutectic composition can be used to promote a uniform, dimple-free Al melt. We have also investigated the kinetics of stratification of the back-contacts into various regions: P+, eutectic, and molten (but unconnected) Al particles. The properties of these regions are primarily dictated by the temperature ramp-down profile, and they strongly depend on incident light flux that heats the wafer, on thickness of Al, and on emissivity of the Al-Air interface. We will discuss methods to improve back-contact properties of screen-printed multi-crystalline Si solar cells.
Keywords :
aluminium; diffusion; electrical contacts; elemental semiconductors; liquid metals; semiconductor-metal boundaries; silicon; solar cells; thick films; Si-Al; back contact; diffusion; dimple-free melt; eutectic composition; eutectic particles; fire-through process; incident light flux; molten particles; screen-printed multi-crystalline solar cells; stratification kinetics; temperature ramp-down profile; Artificial intelligence; Contact resistance; Gettering; Impurities; Ohmic contacts; Optical reflection; Photovoltaic cells; Silicon; Surface resistance; Temperature;
Conference_Titel :
Photovoltaic Specialists Conference (PVSC), 2009 34th IEEE
Conference_Location :
Philadelphia, PA
Print_ISBN :
978-1-4244-2949-3
Electronic_ISBN :
0160-8371
DOI :
10.1109/PVSC.2009.5411536