Very Thin (56 μm) Silicon Heterojunction Solar Cells with an Efficiency of 23.3% and an Open‐Circuit Voltage of 754 mV
Hitoshi Sai, Hiroshi Umishio, Takuya Matsui
Abstract
The silicon heterojunction (SHJ) is a crystalline silicon (c‐Si) solar cell device architecture capable of achieving high efficiencies due to excellent surface passivation realized by hydrogenated amorphous silicon (a‐Si:H) thin layers. The SHJ architecture also allows to process thinner Si wafers due to the structural symmetry and the low processing temperature. Herein, an attempt to increase the performance of very thin c‐Si solar cells is made, using an advanced SHJ architecture. By replacing the conventional a‐Si:H by hydrogenated nanocrystalline silicon (nc‐Si:H) in the hole contact layer, an increase in all solar cell parameters over a wide range of wafer thicknesses from 50 to 400 μm is observed. This also provides an open‐circuit voltage ( V OC ) of 754 mV with the very thin absorber, which is the highest V OC independently confirmed under standard test conditions (STCs) among any c‐Si solar cells ever reported. As a result, a notable efficiency of 23.27% is realized in a SHJ cell with an average thickness of only 56.2 μm. These results demonstrate the high potential of very thin c‐Si solar cells that may open various opportunities for flexible and lightweight c‐Si modules, as well as reducing the carbon footprint of solar cell manufacture.