Robust AZO/i-ZnO bilayer front contact for high-performance thin film solar cells

Abstract

Aluminum-doped zinc oxides (AZOs) and AZO/i-ZnO films were deposited on Corning 7059 glass through a radio-frequency magnetron sputtering method. Films were annealed in CdCl₂ atmosphere and dry air at 400 °C for 60 minutes. The electric properties of the AZO/i-ZnO bilayers demonstrated robustness to the standard CdCl₂ treatment process. The optical band gap and transmittance of the AZO/i-ZnO film showed minimal change after annealing. These properties suggest that the bilayer is more suitable than single AZO film for a transparent conductive oxide (TCO) in CdTe. Moreover, the CdTe-related solar cells that adopted AZO/i-ZnO as a TCO electrode displayed a good performance with higher V_OC and FF than those that that used AZO. The optimal efficiency was 12.65% with AZO/i-ZnO as a front contact.