Abstract
We investigated high-efficiency two-terminal tandem photovoltaic (PV) devices consisting of a p/i/n thin film silicon top sub-cell (p/i/n-TFS) and a heterojunction with an intrinsic thin-layer (HIT) bottom sub-cell. We used computer simulations and experimentation. The short-circuit current density (Jsc) of the top sub-cell limits the Jsc of the p/i/n-TFS/HIT tandem PV device. In order to improve the Jsc of the top sub-cell, we used a buffer-layer at the p/i and i/n interface and a graded forward-profile (f-p) band gap hydrogenated amorphous silicon germanium active layer, namely i-layer, in the top sub-cell. These two approaches showed a remarkable raise of the top sub-cell’s Jsc, leading to the increase of the Jsc of the PV tandem device. Furthermore, in order to minimize the optical loss, we employed a double-layer anti-reflective coating (DL-ARC) with a magnesium fluoride/indium tin oxide double layer on the front surface. The reduction in broadband reflection on the front surface (with the DL-ARC) and the enhanced optical absorption in the long wavelength region (with the graded f-p band gap) resulted in the high Jsc, which helped achieve the efficiency up to 16.04% for inorganic-inorganic c-Si-based tandem PV devices.
Highlights
In a tandem c-Si-based configuration, designers use c-Si having a band gap of around 1.1 eV as the bottom sub-cell, while the top sub-cell should have a band gap in the range of 1.4–1.8 eV7,8
We report a tandem solar cell having a buffer-layer at the (p/i and i/n) interfaces and band gap profiling of the active i-layer in the top sub-cell
The power conversion efficiency (PCE) of the optimized p/i/n-TFS/heterojunction with an intrinsic thin-layer (HIT) tandem solar cell showed the Jsc of up to 15.19 mA/cm[2] and an efficiency of 16.04%, representing the highest PCE to date of the tandem solar cell based on an inorganic-inorganic c-Si-based tandem solar cell
Summary
Jinjoo Park[1], Vinh Ai Dao[2,3], Sangho Kim[4], Duy Phong Pham[1], Sunbo Kim[4], Anh Huy Tuan Le1, Junyoung Kang1 & Junsin Yi1. Both organic-inorganic (perovskite/c-Si multi-junction) and inorganic-inorganic [p/i/n thin film silicon (p/i/n-TFS)/c-Si multi-junction] solar cell configurations have been investigated widely to achieve these band gap ranges[3,5,7,8,9,10,11] In these devices, the tunneling-recombination junction plays a significant role in enhancing power conversion efficiency (PCE)[9]. We investigated the effects of the materials, the band gap profiles (interface and active i-layer), and the DL-ARC on the Jsc. The PCE of the optimized p/i/n-TFS/heterojunction with an intrinsic thin-layer (HIT) tandem solar cell showed the Jsc of up to 15.19 mA/cm[2] and an efficiency of 16.04%, representing the highest PCE to date of the tandem solar cell based on an inorganic-inorganic c-Si-based tandem solar cell
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