Product Briefing Outline: BASF has extended its range of process chemicals for the manufacture of solar cells with a new, environmentally-friendly cleaning solution, ‘SELURIS’ Clean. It enables efficient hydrophilicity, i.e. the targeted modification of surface activity, as well as subsequent cleaning and passivation of the solar cell wafers. Additionally, SELURIS Clean can also be used at lower temperatures enabling lower processing costs.
Problem: Obtaining the correct wafer conditions before the doping process enables improved doping uniformity and cell performance. Post doping cleaning also reduces the occurrence of undesired electrical errors, which would otherwise result in reduced solar cell performance.
Solution: Before doping, the cut and texturized silicon wafers must be rendered hydrophilic. This allows improved surface wetting and therefore more homogenous distribution of the phosphoric acid on the wafer. This, in turn, later results in an optimum solar cell performance. After doping, SELURIS® Clean primarily acts as an efficient cleaning agent. Any unwanted residual phosphorous remaining on the surface is removed quickly and easily. This is also referred to as improved passivation of the wafer surface.
Applications: The chemical is used twice in the manufacturing process for cleaning and passivation of solar cells – both before and after the phosphoric acid doping procedure.
Platform: Part of the SELURIS range are etching and texturizing chemicals, which enable saw damage to be rectified and the wafer surfaces to be structured. In addition, the portfolio also includes high-purity phosphorus oxychloride (POCl3) for subsequent wafer doping.
Availability: March 2009 onwards.
