INDHI Programme

The solar cell industry has experienced significant growth in recent years. Looking to provide an advantage to European producers, the INDHI programme supported a three-year R & D project aimed at increasing cell efficiency. The INDHI project has developed the corresponding industrial processes for massive solar cell production. Better solar cells, industrially fabricated, will substantially increase the use of solar energy.

The Institut fûr Solarenergie Forschung (ISFH), a German partner in the INDHI project, was called upon to determine the robustness of silicon nitride (SiN x ) layers. Laboratory measurements of the INDHI prototype revealed excellent results for the bulk lifetime parameter. In addition, optimal surface passivation was achieved during contact firing with the aid of floating zone silicon (FZSi).

The next phase of the research involved extending the new SiN x technology from a prototype to industrial-scale production. The ISFH collaborated with fellow INDHI partners EniTechnologie and the Italian National Agency for New Technologies, Energy and the Environment to produce a batch of 24 wafers. The result was an efficiency rating of 15.1 %. A second production run was performed with the Universität Konstanz, which introduced a short circuit current that helped boost the efficiency to 15.9 %.

The ISFH subsequently subjected the new SiN x wafers to significant doses of ultraviolet radiation to ensure reliability in the field. Further tests revealed that surface passivation and other critical wafer properties were preserved during the move from the laboratory to an industrial production set-up. The ISFH and its INDHI partners are following up on these promising results.

The selective emitter is the backbone of any solar cell. It is the quality of this selective emitter that basically determines solar cells' efficiency. The INDHI project partners have successfully developed a novel screen-printed selective emitter for industrial multi-crystalline silicon solar cells. The emitter has been fabricated with selective printing on the substrate material of doped pastes.

INDHI project partners used the commercially available Soltech P101 thick film dopant paste for the formation of the emitter. Several selective emitters have been obtained with resistance values ranging from 20 to 100 Ohms per square centimetre of the emitter's sheet.

The selective emitters formed in this work package of the INDHI project have been extensively optimised and tested. Control of the lateral diffusion of the doped paste, reflectance and characterisation of the properties of the junctions have been among the optimisation parameters. Efficiencies approaching 20 % have been achieved.

(Source ResearchEU)

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