NOVELTY - A photovoltaic device comprises substrate, back contact layer, absorber layer containing p-doped polycrystalline copper indium gallium selenide (CIGS), and n-doped charge-separation/collection layer containing fullerene or quasi two-dimensional (2D) material.    USE - A photovoltaic device.    ADVANTAGE - The CIGS-based solar cell has independently tunable sublayers, reduced parasitic layer absorption, reduced charge recombination effects, higher charge transport capability, improved performance, and lower fabrication and maintenance cost. The device structure results in lower levelized cost of electricity, can reduce interfacial recombination and passivate interfacial traps to enhance open circuit voltage and fill factor, and has higher theoretical conversion efficiency than previous devices.    DETAILED DESCRIPTION - A photovoltaic device comprises substrate, back contact layer, absorber layer containing p-doped polycrystalline CIGS (CuIn1-xGaxSe2), and n-doped charge-separation/collection layer containing fullerene or quasi 2D material.    x=0.3-1.    INDEPENDENT CLAIMS are included for:    (1) photovoltaic device comprising substrate, back contact layer, absorber layer made from p-doped polycrystalline CIGS, n-type electron extraction layer, and organic-based hole blocking layer;    (2) manufacture of photovoltaic cell which involves depositing back contact layer on surface of substrate, depositing p-type polycrystalline CIGS absorber layer on surface of back contact layer, depositing insulating layer or passivation layer on surface of absorber layer opposite to back contact layer, and transferring graphene monolayer on a surface of insulating layer or a surface of passivation layer without damaging absorber layer;    (3) conversion of light to electric current which involves exposing photovoltaic device to light;    (4) production of n-doped graphene which involves contacting 1st surface of p-doped semiconductor material with alkaline metal-containing substrate, which is optionally coated with back contact layer, and contacting 2nd surface of p-doped semiconductor material with graphene, which is not n-doped before contact, in which 2nd surface of p-doped semiconductor material is optionally coated with insulating layer or passivation layer;    (5) production of n-doped graphene which involves contacting alkaline metal-containing substrate with graphene, which is not n-doped before contact, in which alkaline metal-containing substrate contains alkaline in an amount effective to produce n-doped graphene; and    (6) article of manufacture comprising the n-doped graphene.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram of the CIGS-based solar cell with a quasi-2-dimensional electron extracting layer and organic hole blocking layer.