NOVELTY - The method comprises: blanket depositing a doped liquid precursor including dopants on a surface (101a) of a substrate wafer (101) to create a doped film (104) on the surface of the substrate wafer; selectively forming a diffusion source in the doped film to selectively diffuse the dopants into the substrate wafer; and heating the doped film on the substrate wafer. The heating step diffuses the dopants from the doped film into the substrate wafer. The step of selectively forming the diffusion source comprises selectively curing the doped film on the surface of the substrate wafer.    USE - The method is useful for selectively diffusing dopants into a substrate wafer (claimed) that is useful in a silicon solar cell.    ADVANTAGE - The method allows selective heavy doping of the emitter region under metal contacts to obtain low contact resistance for metal and to repel minority carriers from the metal contacts, selective light doping on the rest of the emitter region to achieve low surface recombination, low emitter dark current, higher lifetime of the emitter region and an improved spectral response for light absorbed in the emitter region, dual doping of the wafer, and selective heavy doping to form high-low junctions on the back of the semiconductor device or back contact regions on the solar cells, thus increasing the efficiency of the silicon solar cells.    DETAILED DESCRIPTION - The method comprises: blanket depositing a doped liquid precursor including dopants on a surface (101a) of a substrate wafer (101) to create a doped film (104) on the surface of the substrate wafer; selectively forming a diffusion source in the doped film to selectively diffuse the dopants into the substrate wafer; and heating the doped film on the substrate wafer. The heating step diffuses the dopants from the doped film into the substrate wafer. The step of selectively forming the diffusion source comprises selectively curing the doped film on the surface of the substrate wafer. The diffusion of the dopants from the doped film into the substrate wafer comprises simultaneous creation of heavily-diffused regions and lightly-diffused regions on the substrate wafer. The method further comprises: creating a lightly-diffused region in the substrate wafer after the depositing step or prior to the depositing step; heating the selectively-cured doped film to convert the selectively-cured doped film into silicon compounds; selectively oxidizing the selectively-cured doped film to create non-oxidized cured regions (104a) and oxidized uncured regions (104b) of the selectively-cured doped film; and doping a liquid precursor with dopants to form the doped liquid precursor. The doped film is selectively cured by patterned irradiation. The dopants are one of positive-type impurities or negative-type impurities. The depositing step is performed by ink-jet printing, screen printing, condensing, pneumatic spraying, ultrasonic spraying, electro spraying, spraying by liquid ejection from an orifice, spraying by direct injection of droplets of the doped liquid precursor impinging on the substrate wafer, spin coating, roller coating, bar coating, curtain coating, dip coating, or bar coating. The doped liquid precursor is photo-sensitive and heat-sensitive.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic sectional view of a selectively oxidized doped polysilane film on a surface of the substrate wafer.    Substrate wafer (101)    Surface (101a)    Doped film (104)    Non-oxidized cured regions (104a)    Oxidized uncured regions. (104b)