TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Property: The first photoactive subcell layer has a bandgap of 0.7-1.4 eV. Preferred Component: The substrate is a second photoactive subcell layer having second-subcell lattice parameter different from the first-subcell lattice parameter and sensitive to a second photoactive-subcell-layer wavelength. The buffer layer is transparent to light of the second-photoactive-subcell-layer wavelength.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Component: The Group III element comprises gallium and indium, and the Group V element other than nitrogen comprises arsenic. The first photoactive subcell layer has a composition comprising gallium, indium, arsenic, and nitrogen. The indium is present in the first photoactive subcell layer in an amount of 7-32 atm.%, and nitrogen is present in the first photoactive subcell layer in an amount of 0-2.5 atm.%. Preferred Composition: The first photoactive subcell layer has a composition in the form of Ga1-%-InIn%-InAs1-%-N%-N, where % In(a-OEg)=alpha-Ina-O+beta-In3Eg+gamma-In and %N(a-OEg)=alpha-Na-O+beta-NEg+gamma-N.a-O=angstrom;E-G=electron volts;alpha=192.72;beta-In=-15.41;gamma-In=-1067.6;alpha-N=-20.21;beta-N= -6.12;gamma=122.88.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Component: The Group III element comprises gallium and indium, and the Group V element other than nitrogen comprises arsenic. The first photoactive subcell layer has a composition comprising gallium, indium, arsenic, and nitrogen. The indium is present in the first photoactive subcell layer in an amount of 7-32 atm.%, and nitrogen is present in the first photoactive subcell layer in an amount of 0-2.5 atm.%. Preferred Composition: The first photoactive subcell layer has a composition in the form of Ga1-%-InIn%-InAs1-%-N%-N, where % In(a-OEg)=alpha-Ina-O+beta-In3Eg+gamma-In and %N(a-OEg)=alpha-Na-O+beta-NEg+gamma-N.a-O=angstrom;E-G=electron volts;alpha=192.72;beta-In=-15.41;gamma-In=-1067.6;alpha-N=-20.21;beta-N= -6.12;gamma=122.88.