Outstanding Surface Passivation for Highly Efficient Silicon Solar Cells Enabled by Innovative Al<sub><i>y</i></sub>TiO<sub><i>x</i></sub>/TiO<sub><i>x</i></sub>Electron‐Selective Contact Stack
Mohamed M. Shehata, Pheng Phang, Rabin Basnet, Yanting Yin, Felipe Kremer, Gabriel Bartholazzi, Gunther G. Andersson, Daniel Macdonald, Lachlan E. Black
Abstract
Passivating contacts based on transition metal oxides (TMOs) have the potential to overcome existing performance limitations in high‐efficiency crystalline silicon (c‐Si) solar cells, which is a significant driver for continuing cost/Watt reductions of photovoltaic electricity. Herein, innovative stacks of Al‐alloyed TiO x (Al y TiO x ) and pure TiO x as transparent electron‐selective passivating contacts for n‐type c‐Si surfaces are explored. An optimized stack of 2 nm Al y TiO x and 2 nm TiO x is shown to provide both record‐quality surface passivation and excellent electrical contact, with a surface recombination current density prefactor J 0 of 2.4 fA cm −2 and a specific contact resistivity ρ c of 15.2 mΩ cm 2 . The performance of this innovative stack significantly exceeds previously reported values for pure or doped TiO x single layers, SiO x /TiO x stacks, a‐Si:H/TiO x stacks, and other transparent contact technologies. Furthermore, an excellent efficiency of 21.9% is attained by incorporating the optimized stack as a full‐area rear contact in an n‐type c‐Si solar cell. The findings set a new benchmark for the passivation performance of metal oxide‐based passivating contacts, bringing it to a level on par with state‐of‐the‐art SiO x /poly‐Si contacts while greatly improving optical transparency.