Textured and micropillar silicon heterojunction solar cells with hot-wire deposited passivation layers

The passivating quality of hydrogenated amorphous silicon thin films is essential for achieving high open-circuit voltages in silicon heterojunction solar cells. This work reports our progress towards the use of hot wire chemical vapor deposition for fabricating these passivation layers. We have achieved 19.4% energy conversion efficiency for a solar cell with a conventional alkali-etched pyramidal texture. Next, we tested radial heterojunction devices that consist of up to 20-μm high micropillar arrays. Proper passivation of these devices is challenging, since the structures feature an enlarged surface area and vertical walls. We have made use of the ability of hot wire chemical vapor deposition to deposit conformal thin films at high deposition rate. The micropillar solar cells show only limited reduction of open-circuit voltage in comparison to a flat reference solar cell and have an improved overall performance. We created additional stacked multijunction silicon-based junctions on top of the micropillars to increase the open-circuit voltage of the solar cells for future applications in which a higher potential is required such as water splitting devices.