Lithographic fabrication of point contact with Al2O3 rear-surface-passivated and ultra-thin Cu(In,Ga)Se2 solar cells

Atomic layer deposition of Al2O3 was used to fabricate rear surface passivation with lithographed point contact Cu(In,Ga)Se-2 (CIGS) solar cells. We successfully demonstrated the use of photolithography to fabricate point contact holes of small size and fine pitch. The efficiency of the Al2O3 rear-surface-passivated ultra-thin CIGS solar cells with absorber layers of 1.89 mu m and with a 5-nm-thick Al2O3 rear surface passivation layer and local point contact holes with a pitch of 1 mu m and a diameter of 500 nm was 19.3% (total area=0.519 cm(2)). The efficiency of the Al2O3 rear-surface-passivated ultra-thin CIGS solar cells with absorber layers of 380 nm was 11.3% (active area=0.514 cm(2)) when an antireflection layer was used. Compare with unpassivated CIGS solar cells, higher efficiencies were found for the Al2O3 rear-surface-passivated CIGS solar cells, mainly due to the reduced carrier recombination and enhanced rear internal light reflection.