PP1.2 Rear Contact Silicon Cells
N-type silicon has many advantages for solar cells, but hitherto has not been widely used in the industry. It has reduced sensitivity to metallic impurities such as iron, and long diffusion lengths. It is the material used for record efficiency but relatively high-cost commercial cells made by SunPower and Sanyo/Panasonic. There is substantial scope for further process simplification while retaining or increasing the efficiencies of these cells.
In this part of the Program Package (PP1.2), we will use back-contact n-type cells as the workhorse for the testing of improved techniques for n-type silicon. Back contact cells have high efficiency potential due to the absence of front metal contacts. The research will include the development of hybrid cell structures, combining the heterojunction technology of Panasonic with technology for localized doping, and double sided contacted, rear junction cells. Development of greatly simplified process techniques have been developed in the first 4 years, leading to superior cell efficiency at a cost similar to that of conventional p-type screen printed solar cells. In later years, efficiencies above 25% are targetted.
Also as part of this Program Package, the laser based selective doping approaches originally developed at UNSW will be applied to both n- and p-type substrates in an attempt to reach similar performance levels as an alternative approach to reach such performance levels.