Texture and morphology variations in (In,Ga)₂Se₃and Cu(In,Ga)Se₂thin films grown with various Se source conditions

Texture and morphology variations in co‐evaporated (In,Ga) 2 Se 3 and Cu(In,Ga)Se 2 (CIGS) films grown with various Se source conditions during growth were studied. The Se species of simply evaporated, large molecular Se (E‐Se, low‐sticking coefficient), and RF‐plasma cracked atomic Se (R‐Se, high sticking coefficient) were used in the present work. (In,Ga) 2 Se 3 precursor films, which were prepared during the first stage of CIGS film growth by the three‐stage process, showed systematic variations in texture and Na distribution profile with varying evaporative Se (E‐Se) flux. The properties of CIGS films and solar cells also showed systematic variations, and the open‐circuit voltage ( V oc ) and fill factor were found to be especially sensitive to the E‐Se flux. R‐Se grown (In,Ga) 2 Se 3 precursor films featured granular morphology with strong (105) and (301) peaks in the diffraction pattern, and the texture was very similar to an E‐Se grown film fabricated with a Se to group III metal (In + Ga) flux ratio ( P [Se]/[In + Ga] ) of about 6, although the nominal P [Se]/[In + Ga] used for an R‐Se source was very small and less than 0.5. The R‐Se grown CIGS films displayed, however, highly dense surfaces and larger grain sizes than E‐Se grown CIGS films. The controllability of film morphology and the Na diffusion profile in (In,Ga) 2 Se 3 and CIGS films with various Se source conditions are discussed.