Andreas Schneider

Bow reducing factors for thin screenprinted MC-Si solar cells with Al BSF

Silicon solar cell costs could be strongly reduced by the use of thinner wafers. However, thin wafers are susceptible to bowing caused by the influence of the metallisations on the front and rear side. Excessively bowed wafers lead to unacceptable yield losses during module construction. Screen printed aluminium paste is the major contributor to bowing which increases with decreasing wafer thickness. One barrier to using thinner wafers is the lack of an aluminium paste that combines good doping conditions for the BSF, good ohmic contact properties with a composition that has low bowing tendencies. In this work, we studied the effect of Al print thickness on electrical and mechanical performance of new aluminium pastes, developed by DuPont, using 200 /spl mu/m thick 12.5/spl times/12.5 cm wafers. The influence of aluminium paste composition, firing conditions and silver front side was also studied.

Comparison of gettering effects during phosphorus diffusion for one- and double-sided emitters

A key issue for future solar cell processes is a diffusion sequence which enables fast and clean production, for example by spin-on and spray-on dopants. These diffusion processes have in common that the emitter diffusion is applied on one wafer side, whereas the POCl/sub 3/ emitter process leads to double-sided doping. For higher throughput the POCl/sub 3/ process could be adapted by using one slot for two wafers. This so called back-to-back process leads to one-sided emitters and increases industrial throughput but could result in lower cell efficiency due to reduced gettering during phosphorus diffusion. In this study we investigate the difference in solar cell performance for cells processed in a back-to-back and standard POCl/sub 3/ process. Furthermore, X-ray fluorescence and SIMS measurements were performed on Cz material to study the effect of emitter over-compensation by aluminium. These experiments should clarify if the phosphorus of double-sided emitter cells is partly overcompensated or diffuses into the Al layer of the rear contact.

Evaluation of cell to module losses for n-type IBC solar cells assembled with state of the art consumables and production equipment

In this paper we present an investigation on different aspects of the module assembly for back contacted n-type solar cells; in our case implemented on ISCs “Zebra” IBC cell. With all contacts on the rear, new possibilities and challenges arise. The study is conducted on one cell mini-modules, “rear half”- and “front half”- mini-modules. It is aiming to minimize the overall cell to module (CTM) loss and to maximize module robustness against climate chamber tests. Electrical losses are evaluated using different interconnection schemes whereby optical losses are studied by utilizing novel encapsulant layers; long term stability is probed with climate chamber testing (TC200/400), PID and surface polarization tests.