Solution-processed molybdenum oxide for hole-selective contacts on crystalline silicon solar cells

Abstract

Sub-stoichiometric molybdenum oxide (MoOx) films are commonly deposited on crystalline silicon (c-Si) solar cells by thermal evaporation, a process that requires high vacuum and provides limited control of oxide stoichiometry and in consequence limited control of hole transport properties. Here, we report on a method of forming MoOx films on crystalline silicon wafer surfaces by spin-coating hydrogen molybdenum bronze solutions. It is shown that a ∼2.8nm thick interfacial SiOx layer forms under the spin-coated MoOx films and that the as-deposited MoOx is amorphous and sub-stoichiometric (x=2.73), with the concentration of oxygen vacancies in the MoOx being able to be reduced by annealing in air. The as-deposited MoOx films show comparable contact resistivity and passivation quality on c-Si wafers to thermally-evaporated MoOx, demonstrating their potential to be an effective hole-selective contact layer for c-Si solar cells and an alternative for thermally-evaporated films.