NOVELTY - The method comprises: providing a doped silicon substrate having a front, sunward facing, surface and a rear surface; forming a silicon dioxide layer on the front surface and the rear surface; depositing a boron-containing doping paste comprising a boron compound and a solvent on the rear surface in a pattern; depositing a phosphorus-containing doping paste comprising a phosphorus compound and a solvent on the rear surface in a pattern; and heating the silicon substrate to locally diffuse boron and phosphorus into the rear surface of the silicon substrate.    USE - The method is useful for manufacturing a photovoltaic cell such as interdigitated back contact solar cell, with a locally diffused rear side (all claimed).    ADVANTAGE - The method is capable of forming high efficiency interdigitated back contact solar cell, and introducing an oxide layer prior to printing patterned doping pastes so as to allow for simultaneous boron and phosphorus diffusion into the underlying wafer and at the same time to eliminate unintended doping onto neighboring silicon surfaces.    DETAILED DESCRIPTION - The method comprises: providing a doped silicon substrate having a front, sunward facing, surface and a rear surface; forming a silicon dioxide layer on the front surface and the rear surface; depositing a boron-containing doping paste comprising a boron compound and a solvent on the rear surface in a pattern; depositing a phosphorus-containing doping paste comprising a phosphorus compound and a solvent on the rear surface in a pattern; and heating the silicon substrate in an ambient to a first temperature and for a first time period in order to locally diffuse boron and phosphorus into the rear surface of the silicon substrate. The method further comprises: removing the silicon dioxide layer from the silicon substrate; forming a passivation layer on both the front surface and the rear surface of the substrate; and forming a first electrode and a second electrode on the rear surface, where the first electrode is in electric contact with a first region of the silicon substrate where boron is locally diffused, and the second electrode is in electric contact with a second region of the silicon substrate where phosphorus is locally diffused. The whole outer surface of the silicon substrate is oxidized during the silicon dioxide layer forming step. The depositing steps are carried out to deposit boron-containing doping paste and the phosphorus-containing doping paste on the silicon dioxide layer on the rear surface of the substrate, respectively, where the boron and phosphorus are diffused into the rear surface of the silicon substrate through the silicon dioxide layer. The silicon dioxide layer forming step is carried out by one of thermal oxidation, printing and drying a composition comprising silicon dioxide particles, chemical vapor deposition, chemical oxidation, steam oxidation, printing and oxidizing a composition comprising of silicon particles, or growing and oxidizing a porous silicon layer. A thickness of the silicon dioxide layer is between 10-100 nm. A doped layer is formed on the front surface of the silicon substrate prior to the silicon dioxide layer forming step, where the doped layer is doped with the same dopant as the dopant of the silicon substrate. Another doped layer is formed on the front surface of the silicon substrate after removing the silicon dioxide layer and before forming the passivation layer, where the latter doped layer is doped with the same dopant as the dopant of the silicon substrate. The first temperature is 850-1000 degrees C, and the ambient is nitrogen and/or oxygen. The photovoltaic cell comprises a p+ diffusion area and an n+ diffusion area on the rear surface of the silicon substrate. The cell further comprises a first metal electrode in ohmic contact with the p+ diffusion area and a second metal electrode in ohmic contact with the n+ diffusion area.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of an interdigitated back-contact solar cell.    Phosphorus doped silicon substrate (201)    Boron emitter (202)    Dielectric layers (205, 206)    Boron emitter metal contacts (207)    Back surface field metal contacts. (208)