Simultaneous dopant diffusion and surface passivation in a single rapid thermal cycle

Abstract

In this work, we present results on simultaneous formation of emitter/back‐surface field or emitter/surface passivation in a single rapid thermal cycle. We have investigated the diffusion kinetics of dopant elements like phosphorus, boron (from a doped spin‐on glass (SOD) film), aluminium (from evaporated films) or aluminium‐boron (from an A1‐B SOD film). In particular, we have shown that rapid thermal co‐diffusion of P and A1 (or A1‐B) leads to low sheet resistances, optical emitter profiles and a hig h gettering effect. Furthermore, the possibility of using the remaining SOD films as a surface passivation layer was investigated. Dark saturation current measurements as deduced from the photoconductivity decay technique demonstrate the passivation effec t of the remaining SOD film. The highest efficiency of 12.8% obtained was achieved on SOD oxide‐coated solar cells.

Silicon PV devices based on a single step for doping, anti-reflection and surface passivation

“…We believe that the mildly oxidizing atmosphere in which the doping is carried out aides the growth of a thin interfacial oxide, leading to passivation of surface dangling bonds or the oxide in the SOD film passivates the surface. Similar passivation schemes have also been shown to reduce emitter saturation current density, which is a direct indicator of passivation [9,10]. It can also be seen that open circuit voltage for the chemically textured Fz sample is reduced by about 20 mV as compared to the non-textured case.…”

“…Lachiq et al [10] reported a fabrication scheme where the authors used a spin on dopant solution to obtain diffusion with a rapid thermal annealing process in an inert atmosphere. The authors retained the thin ( o20 nm) SOD film to serve as a surface passivation layer with further need for an ARC.…”

Boron Diffusion with Boric Acid for High Efficiency Silicon Solar Cells

“…2 Previously, boron diffusion into Si has been achieved using liquid BBr 3 , solid sources, spin-on sources, and SP pastes. [3][4][5][6][7] The BBr 3 source has been used to fabricate very high efficiency solar cells; however, BBr 3 is a hazardous chemical and requires an extra masking step to allow diffusion only on one side of the sample. 3 Solid sources, spin-on sources, and pastes are simpler and safer alternatives, but degrade the bulk lifetime.…”

A Novel Processing Technology for High‐Efficiency Silicon Solar Cells

“…Historically, the simultaneous diffusion of boron and phosphorus in silicon has been implemented in several ways. For example, using boron and phosphorus spin-on dopants (SOD) films, boron and phosphorus can be simultaneously diffused in a rapid thermal processor 2 or in a conventional diffusion furnace, 3 without significant cross-doping. The drawbacks of this approach are that the wafers are left with a thick diffusion glass which in most cases must be removed in order to apply an effective antireflection coating, thus eliminating any potential for in situ oxide surface passivation.…”