Balance of efficiency and stability of silicon heterojunction solar cells

Consideration must be given to both surface passivation and stability for the design of intrinsic hydrogenated amorphous silicon (a-Si:H(i)) films for silicon heterojunction (SHJ) solar cells. Although the underdense a-Si:H(i) films could offer outstanding surface passivation and lead to a high cell efficiency, it was hard for such a porous structure to prevent the intrusion of sodium-ion (Na+) and moisture during Na+ aging test, resulting in the serious degradation of cell efficiency. Hence, we replaced the a-Si:H(i) film at the sun side with the a-SiOx:H(i) film and applied 20-s hydrogen plasma treatment to the underdense a-Si:H(i) film at the rear side in order to reduce the porosity of the a-Si:H(i) films without epitaxial growth. Additionally, an 80-nm SiOx layer was capped on the rear side of the optimized SHJ solar cells as a protective layer, leading to a high efficiency of 22.23% and the negligible degradation of only 0.27%abs after 3-h Na+ aging test. This work offers a valid approach to balancing both the high efficiency and high stability of SHJ solar cells, which may guide the optimization of SHJ solar cells for real applications. •Different structure and porosity of a-Si:H(i) films are applied in SHJ solar cells.•Na+ aging test is to assess the stability of cells encapsulated by soda-lime glass.•Dense a-SiOx:H(i) films suppress epitaxy and provide better Na+ damp-heat stability.•H2 plasma treatment reduces porosity of a-Si:H(i) films and improves cell stability.•This work offers a strategy to balances efficiency and stability of SHJ solar cells.