Properties of GaAs solar cells coated with diamondlike carbon films

Thin films of amorphous diamondlike carbon (a:DLC) were deposited on GaAs solar cells, with and without antireflecting coating. The films were deposited by decomposition of CH4 plasma using a r.f. generator (13.56 MHz). The reflected light from these cells, in the visible light, decreased after deposition of a:DLC film thickness (from 33% for t = 0 nm to 14% for r = 60 nm) which indicates antireflecting properties. The I-V measurements show an increase of the short circuit current (I-sc) with films thickness up to t similar to 40-60 nm, where it reaches a maximum and then decreases for higher thickness (r > 60 nm). The efficiency (eta) of the cells, as a function of the a:DLC thickness, shows a maximum value of similar to 15% for t = 50 nm. It was also shown, that the a:DLC films is a useful material as a protecting material for cells for operation in an abrasive environment. In abrasive environment, the efficiency of the coated cell maintains the level of about 12% whereas the efficiency of uncoated cells drop sharply from 15.5% to 6%. (C) 1998 Elsevier Science S.A. All rights reserved.