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.