Screen printing of CdS pastes for CdS-based solar cells

The screen-printing properties of slurries made with three organic binders are discussed. They are ethyl cellulose (EC), glycerol, and propanediol (PD). A procedure is described to meet the requirements for the removal of ethyl cellulose (oxygen required) and the sintering of the CdS film (oxygen absolutely to be avoided). It is observed that no good quality CdS screen prints are obtainable with a PD-slurry. It is also clear from the results that the choice of an optimal set of screen printer settings can give only minor improvements. The composition of the slurry, and more specifically the choice of the organic binder, has far more influence. It is shown that the choice of an ethyl cellulose binder makes it possible to screen print much smoother films, with a sharper edge definition. It is shown that the CdS layer, screen printed from EC-slurries, has the same electrical and morphological properties as the films printed from a PD-slurry.