Monolithic multicolor solar cells offer the potential of very high energy conversion efficiencies for concentrated sunlight systems. The development of these cells will require the sequential fabrication of low and high band gap junctions in a continuous process system. This paper describes the fabrication of GaAs (0.82)P(0.18) solar cells via vacuum metalorganic chemical vapor deposition (MO-CVD) and their evaluation. GaAs (0.82)P(0.18) junctions can be used for the high band gap junction in multicolor cells, and the vacuum MO-CVD system is a potential continuous process system for these cells. Shallow homojunction GaAs (0.82)P(0.18) cells with active area efficiencies of 14.8% at 7.4 suns are obtained despite a 0.8% lattice mismatch between the cell active layers and the GaAs substrate.