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

Abstract

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 i 2 /i 1 thickness ratio of 6 exhibits a maximum efficiency of 9.0% with the open-circuit voltage (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mi>V</mml:mi></mml:mrow><mml:mrow><mml:mtext>oc</mml:mtext></mml:mrow></mml:msub></mml:math>) of 1.59 V, short-circuit current density (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mi>J</mml:mi></mml:mrow><mml:mrow><mml:mtext>sc</mml:mtext></mml:mrow></mml:msub></mml:math>) of 7.96 mA/cm 2 , 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%.