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)Se2 (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 μm and with a 5-nm-thick Al2O3 rear surface passivation layer and local point contact holes with a pitch of 1 μm and a diameter of 500 nm was 19.3% (total area = 0.519 cm2). 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 cm2) 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.