^aLaboratory of Materials, Energy and Control, Faculty of Sciences and Technology, University Hassan II of Casablanca, BP 146 Boulevard Hassan II, 20650 Mohammedia, Morocco

^bEquipe de mathématiques & interactions (EMI), FST Béni-Mellal, université Sultan Moulay Slimane, Maroc

^cLaboratory Instrumentation Measurements and Control, University Chouaib Doukkali, El Jadida, Morocco

^dResaerch Laboratory in Physicas and Sciences for Engineers (LRPSI), Polydisciplinary Faculty, Sultan Moulay Slimane University, Beni Mellal, Morocco

^eLaboratoire Interdisciplinaire de Recherche en Bio-Ressources, Environnement et Matériaux, Ecole Normale Supérieure, Marrakech, Maroc

^fEquipe Innovation en Métiers d’Enseignement et de Formation, Expérimentation et Orientation en Sciences, CRMEF, Beni Mellal, Maroc

This study aims to improve and evaluate the external quantum efficiency (EQE) of p-i-n GaAs solar cells. The current densities of minority carriers and the geometrical and physical cell parameters were calculated using the finite difference method. As a result, the EQE simulation findings are extremely close to the experimental data, and a maximum EQE of 57.26 %, with optimum layer thicknesses (µm) of p, i, and n are respectively 0.2,1,4, and n and p layers doping (cm-3) of 1020 cm-3 and 4 × 1017 cm-3. The adding of p+-AlGaAs window layer increases the energy conversion efficiency (%) from 19.41 to 25.45.