Broadband anti-reflection coatings for thin film photovoltaics

Light reflection from the glass surface of thin film photovoltaic (PV) modules is a source of significant energy loss for all types of thin film devices. The reflection at the glass and air interface accounts for ~4% of the total energy. Currently, most of the commercial thin film solar modules are manufactured using a glass superstrate/substrate with no light trapping strategy to reduce the reflection loss. To minimise these losses, a series of broadband multilayer thin film coatings has been designed and tested. Anti-reflection coatings for CdTe, CIGS, perovskite and a-Si thin film PV are presented in this paper. The coatings consist of four to six dielectric layers of alternating thin films of ZrO₂ and SiO₂. The layers were deposited by using a high deposition rate pulsed DC magnetron sputtering tool. Spectrophotometer measurements confirm that the transmission increased by between 2% and 5% over the spectrum utilized by each thin film solar cells. The weighted average reflection reduced from around 4.22% to 0.62% (a-Si-4 layers), 0.80% (perovskite-4 layer), 1.22% (CdTe-4 layers), and 1.49% (CIGS-6 layers). This results in an increase in current density and cell efficiency. These dielectric coatings are highly durable and scratch resistant.