To support the development of low-cost sustainable photovoltaic technologies in countries with limited economic resources but abundant solar radiation (As Benin in West Africa) we investigate in this study physical properties (anode transmittance and active layer absorption) to improve energy conversion performance. The devices fabricated in air yield almost similar performances that those fabricated in N2, confirming that the fabrication process can be carried out in simple environmental conditions. This paper discusses the optical absorption of PCBM([6,6]-phényl-C61-butiryc acid methyl ester) and PC70BM(methano-fullerene-[6,6]-phenyl-C71-methyl butyrate) films spin coated at different velocity and different concentration of P3HT(Poly-3-hexylthiophen). The optimum thickness of the active layer is determined by a compromise between optimization of absorption (thick film) and transportation (thin film). Annealing temperature and duration is the same for different films and this target to improve photovoltaic device performance.