Optimization of Recombination Layer in the Tunnel Junction of Amorphous Silicon Thin-Film Tandem Solar Cells

The amorphous silicon/amorphous silicon (a-Si/a-Si) tandem solar cells have attracted much attention in recent years, due to the high efficiency and low manufacturing cost compared to the single-junction a-Si solar cells. In this paper, the tandem cells are fabricated by high-frequency plasma-enhanced chemical vapor deposition (HF-PECVD) at 27.1 MHz. The effects of the recombination layer and the i-layer thickness matching on the cell performance have been investigated. The results show that the tandem cell with a p+ recombination layer and i2/i1 thickness ratio of 6 exhibits a maximum efficiency of 9.0% with the open-circuit voltage (Voc) of 1.59 V, short-circuit current density (Jsc) of 7.96 mA/cm2, and a fill factor (FF) of 0.70. After light-soaking test, our a-Si/a-Si tandem cell with p+ recombination layer shows the excellent stability and the stabilized efficiency of 8.7%.