Electrophoretically Deposited Thin Films for Low Cost Solar Cells

Summary

The aim of this work is to employ electrophoresis for the deposition of thin semiconductor films suitable for photovoltaic cells. Layers of CdS, CdZnS and Cu_xS have been produced with heterojunctions successfully fabricated.

Progress of the work has been hampered by two major problems. In practice very thin layers prepared by electrophoresis are pinhole free; however, in the course of this work it has been found that small projections on the surface of the deposition electrode lead to micro-cracks on film drying — polishing the substrates has been shown to overcome this. Secondly, the recrystallization and phase transformation of a thin powder film is a non-trivial problem and one that was seriously underestimated at the initiation of this contract. However, after investigations involving a variety of techniques it has been found that pulsed and CW laser radiation offer the means to achieve this.

Heterojunctions have been prepared in several ways, the best results so far being provided by the dry process. In addition a number of novel approaches using laser heating have been investigated and shown to be feasible.

The results obtained to date provide a basis for the production of thin film solar cells at a very low cost with very efficient material usage employing simple technology.