Non-vacuum method for formation of CuIn_0.7Ga_0.3Se₂ absorber thin film using screen printing and far infrared rapid thermal annealing

Chalcopyrite CuIn_0.7Ga_0.3Se₂ (CIGS) has shown to be as an effective absorber in high-efficiency solar cells. Here, a coating paste containing submicron CIGS powders is screen printed on a glass substrate. The printed wet film is then dried and annealed in a far infrared rapid thermal annealing (RTA) system with and without normal loading. The effects of the RTA temperature and normal loading during annealing on the quality of the CIGS films are evaluated. The carrier concentration and mobility of the film increase when the annealing temperature increases from 400°C to 600°C. A three-stage annealing process: 5 min binders/solvents removal at 250°C, 7 min annealing at 500°C, and 3 min densification at 600°C gives a p-T ype chalcopyrite CIGS film with the carrier concentration in the order of 1015 cm-3 when a normal loading of 1.97 N cm^-2 being applied during RTA annealing. There is no carbon being detected in the as-prepared CIGS films after 600°C densification.