A photovoltaic device including a semiconductor substrate having a first surface and a second surface, the second surface being opposite to the first surface; a first passivation layer on the first surface; and a second passivation layer on the second surface, wherein each of the first passivation layer and the second passivation layer comprises an aluminum-based compound, is disclosed. A method of preparing a photovoltaic device, the method including: forming a semiconductor substrate to have a first surface and a second surface, the second surface being opposite to the first surface; forming an emitter region and a back surface field (BSF) region at the second surface; and forming a first passivation layer on the first surface and a second passivation layer on the second surface, wherein the first passivation layer and the second passivation layer are formed concurrently, is also disclosed.