Here we consider how to accurately model and design wide bandgap (Eg = 2.1 eV) GaInP photovoltaic cells. Detailed absorption data for the Ga-rich alloy is obtained by extrapolating literature values for InP and Ga0.5In0.5P. We then combined these values with estimates of carrier lifetime (0.1 ns) and interface recombination (9×105 cm/s) to construct detailed electro-optical models. They are found to accurately reproduce the EQE, Jsc, and Voc observed in published experimental devices. Small discrepancies of 0.1% are caused by slight differences in optical constants and interface recombination. This modeling process illustrates the major sources of loss, namely interface recombination between the emitter and window layer and low bulk minority carrier lifetimes in the active region. An improved design is also proposed, which involves adjusting the doping and thickness of key layers. These findings will help define a path towards increasing the performance of these wide bandgap cells to approach their theoretical limit - approximately 16.5%.