We have applied metallorganic chemical vapor deposition (MOCVD) using less toxic group V-precursors to the fabrication of the monolithic dual-junction GaInP/GaAs and mechanically-stacked GaAs/GaInAs cells, targeting for the super-high-efficiency triple-junction GaInP/GaAs/GaInAs solar cells. The dual-junction GaInP/GaAs cell grown on an n-type GaAs substrate, which is suitable for higher optical transmittance to the bottom cell? showed a conversion efficiency of 25.9% at AM 1.5, 1-sun. Combined with an efficiency of 5.1% for GaInAs bottom cell grown on an InP substrate under the mechanically stacked GaAs top cell, it is possible to attain an efficiency of over 30% by the all organometallic-source MOCVD method. (C) 2001 Elsevier Science B.V. All rights reserved.