NOVELTY - Formation of multijunction solar cell involves providing substrate (101) for epitaxial growth of semiconductor material, forming solar sub-cell (a1) on substrate, forming solar sub-cell (a2) on solar sub-cell (a1), forming ( alpha )-layer (115a)(c1) on solar sub-cell (a2) using surfactant including selenium, forming metamorphic grading interlayer, forming ( alpha )-layer (117a) (c2) using surfactant including selenium, and forming solar sub-cell (a3) on grading interlayer.    USE - Formation of multijunction solar cell used in space application and terrestrial solar power application.    ADVANTAGE - The method enables formation of lightweight multijunction solar cell having high photoconversion efficiency and open circuit voltage, and excellent chemical property, thermal property, manufacturability and handleability, by easy and economical process.    DETAILED DESCRIPTION - Formation of multijunction solar cell involves providing substrate for epitaxial growth of semiconductor material, forming solar sub-cell (a1) on substrate having band gap (b1), forming solar sub-cell (a2) on the solar sub-cell (a1) having band gap (b2) which is smaller than band gap (b1), forming ( alpha )-layer (c1) on solar sub-cell (a2) using a surfactant including selenium, which is configured to prevent threading dislocations from propagating, forming metamorphic grading interlayer on and directly adjacent to barrier layer, forming ( alpha )-layer (c2) using a surfactant including selenium on and directly adjacent to grading interlayer to prevent threading dislocations from propagating, and forming solar sub-cell (a3) on grading interlayer having band gap (b4) smaller than band gap (b2) such that solar sub-cell (a3) is lattice mismatched with respect to solar sub-cell (a2). The multijunction solar cell comprises upper sub-cell, middle sub-cell, and lower sub-cell. The grading interlayer has band gap (b3) greater than the band gap (b2). The grading interlayer comprises different composition than the barrier layer and each of the ( alpha )-layers. The ( alpha )-layer (c2) comprises different composition than the grading interlayer. The grading interlayer is compositionally graded with a lattice constant which matches the lattice constant of the solar sub-cell (a2) on side (d1) and matches the lattice constant of the solar sub-cell (a3) on side (d3). INDEPENDENT CLAIMS are included for the following:    (1) manufacture of solar cell; and    (2) solar cell.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of the solar cell.    Substrate (101)    Buffer layer (102)    Contact layer (104)    Window (105)    Layers (115a,117a)