We report the electrical characteristics of (n)ZnSe/(p(+))GaAs heterostructure solar cells grown by depositing an n-type ZnSe epilayer using photoassisted metal organic vapor phase epitaxy on p(+) type GaAs (100) substrates. A study of the solar cell efficiency as a function of ZnSe epilayer thickness is also presented. Our preliminary results show that an epilayer thickness of 1.5 mum produced the highest efficiency for the cells tested, (4.27% under AM1.5 conditions, no anti-reflective coating). We also demonstrate a method to pattern ZnSe/GaAs structures with an inexpensive methanol/ bromine etch process. (C) 2003 Elsevier Science Ltd. All rights reserved.