In this work, we investigate correlations between optical and electro-optical properties of GaAsPN/GaP p–i–n solar cells grown by MBE on GaP(001) substrates. A photoluminescence model is first proposed to extract the long range compositional fluctuation energy scale from low temperature photoluminescence spectra of the GaAsPN dilute-nitride material. Solar cells grown with the same nitrogen content at different temperature reveal very different electrical performances. A 4.08 mA/cm2 short-circuit current density has been obtained, that is an excellent value given the small absorber thickness (300 nm) and high material bandgap. Comparisons between solar cells photoluminescence, I–V (under AM1.5G illumination) and IQE parameters reveal correlations between their optical and electrical parameters. These results reinforce PL measurements interest for dilute nitride solar cells growth optimization.