ALD grown bilayer junction of ZnO:Al and tunnel oxide barrier for SIS solar cell

Various metal oxides are probed as extrinsic thin tunnel barriers in Semiconductor Insulator Semiconductor solar cells. Namely Al₂O₃, ZrO₂, Y₂O₃, and La₂O₃ thin films are in between n-type ZnO:Al (AZO) and p-type Si substrates by means of Atomic Layer Deposition. Low reverse dark current-density as low as 3×10^-7 A/cm², a fill factor up to 71.3%, and open-circuit voltage as high as 527 mV are obtained, achieving conversion efficiency of 8% for the rare earth oxide La₂O₃. ZrO₂ and notably Al₂O₃ show drawbacks in performance suggesting an adverse reactivity with AZO as also indicated by X-ray Photoelectron Spectroscopy.