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.

c-Si solar cells formed from spin-on phosphoric acid and boric acid

“…Simultaneous emitter/BSF formation in one RTP cycle has been reported with 12.8% efficiency [2]. The simultaneous RTP process significantly reduces thermal budget, cost/efficiency ratio of the solar cell and suitable for industrial mass production.…”

“…By identifying a simple processing condition, reasonable efficiency has been obtained, which does not require high performance features such as anti-reflection coating, rear side patterned dielectric/reflector, local back surface filed, photolithography etc. that are normally required to achieve a comparable performance [2].…”

“…Single-sided spin-on doped/spray doped cells [4e16] with Al-BSF and double-sided spin-on doped cells with boron-BSF has also been reported [2,17,18]. Boron BSF has some advantages over Al-BSF [3,11].…”

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.…”