We report on the study of 1.0 eV InGaAsP solar cells grown by metalorganic vapor phase epitaxy (MOVPE) on InP. Under standard one-sun air-mass 0 (AM0) illumination, InGaAsP single junction solar cell grown at temperature 650 degrees C presents remarkable photovoltaic performance. With further growth improvements, solar cell presents an efficiency of 19.1% with an open-circuit voltage (Voc) of 693 mV. The experimental bandgap-voltage offset (Woc) as low as 325 mV is achieved, approaching its theoretical value predicted using diffusion-limited model.