Hydrogen Molybdenum Bronzes for Hole Transport Layers on Crystalline Silicon Solar Cells

摘要

The stoichiometry of molybdenum oxide (MoO_x) films needs to be controlled to ensure effective hole transport layers. If the layer is too metallic (x = 2) or too insulating (x = 3) then the layer's transport and passivation properties can be impacted. We report on a method of forming MoO_x films on crystalline silicon wafer surfaces by spin-coating hydrogen molybdenum bronze solutions. It is shown that an ~ 2 nm thick interfacial SiO_x layer forms under the spin-coated MoO_x films and that the MoO_x as deposited is amorphous and sub-stoichiometric. Thermal annealing in air reduces the concentration of oxygen vacancies in the MoO_x with stoichiometric films being achieved by annealing at 400 °C. The decay of minority carrier lifetime measurements with time demonstrates the importance of capping the films before measurements for reliable results.