Bilayer MoO/CrO_X Passivating Contact Targeting Highly Stable Silicon Heterojunction Solar Cells

Molybdenum oxide (MoO_X, X < 3) has been successfully demonstrated as an efficient passivating hole-selective contact in crystalline Si (c-Si) heterojunction solar cells because of its large bandgap (∼3.2 eV) and work function (∼6.9 eV). However, the severe performance degradation coming from the instability of the MoO_X and its interfaces has not been well addressed. In this work, we started with a c-Si(p)/MoO_X heterojunction solar cell that yielded a power conversion efficiency (PCE) of 15.86%, in which the MoO_X film was synthesized by industry-compatible atomic layer deposition (ALD). The initial PCE dropped to 10.20% after 2 days because of severe migration of O and Ag at the MoO_X/Ag interface. We solved this by the insertion of a CrO_X layer between the MoO_X layer and the Ag electrode. The solar cell was found to be stable for more than 8 months in air because of the suppression of interface degradation. Our work demonstrates an effective way of improving the stability of silicon solar cells with transition metal oxide carrier selective contacts.