NOVELTY - Photovoltaic device (10) comprises: an absorption layer (12) comprising a silicon-containing semiconductor layer of a first conductivity type and having a top surface and a bottom surface that opposes the top surface; a front contact (24) located on the top surface of the absorption layer; and a back contact (14) located on the bottom surface of the absorption layer, where the back contact comprises at least one back contact semiconductor material layer (18) of the first conductivity type.    USE - The photovoltaic device is useful as a solar cell.    ADVANTAGE - The photovoltaic device has reduced tunneling barrier for hole collection at either the front contact or the back contact of a silicon heterojunction cell, with enhanced efficient, without compromising the surface passivation either the front contact or at the back contact.    DETAILED DESCRIPTION - Photovoltaic device (10) comprises: an absorption layer (12) comprising a silicon-containing semiconductor layer of a first conductivity type and having a top surface and a bottom surface that opposes the top surface; a front contact (24) located on the top surface of the absorption layer; and a back contact (14) located on the bottom surface of the absorption layer, where the back contact comprises at least one back contact semiconductor material layer (18) of the first conductivity type which has a lower band-offset than that of hydrogenated amorphous silicon with crystalline silicon, and/or a higher level of activated doping concentration compared to that of doped hydrogenated amorphous silicon. An INDEPENDENT CLAIM is also included for a photovoltaic device (D1) comprising: the absorption layer; a front contact located on the top surface of the absorption layer, where the front contact comprises at least one front contact semiconductor material layer of a second conductivity type which has a lower band-offset than that of hydrogenated amorphous silicon with crystalline silicon, and/or a higher level of activated doping concentration compared to that of doped hydrogenated amorphous silicon, and the second conductivity type is opposite of the first conductivity type; and the back contact located on the bottom surface of the absorption layer.    DESCRIPTION OF DRAWING(S) - The figure shows a pictorial representation (through a cross-sectional view) depicting a photovoltaic device.    Photovoltaic device (10)    Absorption layer (12)    Back contact (14)    Back contact semiconductor material layer (18)    Front contact (24)