Effect of sulfurization on the microstructure of chalcopyrite thin-film absorbers

Polycrystalline CuInSe2 (CIS) and Cu(In,Ga)Se-2 (CIGS) thin-films were grow n by co-evaporation on a soda lime glass substrate. Rapid thermal processin g (RTP) in H2S atmosphere with processing temperatures ranging from 350 to 550 degreesC was used to sulfurize the absorber. The change in microstructu re after sulfurization and annealing was characterized mainly by transmissi on electron microscopy. A non-uniform and porous surface reaction layer is evident in the CIS and CIGS structures after the RTP. The CIGS structure ha ve a tendency towards a phase separation, whereas, the CIS films exhibit mi xed sulfoselenides, CuIn(Se1-xSx)(2), where x varies. In order to improve t he device performance, the formation of two distinct phases should be avoid ed during the sulfurization processing. (C) 2001 Elsevier Science B.V. All rights reserved.