We investigated photoresponses of AlGaAssolar cells in which coupled GaAsquantum wells were embedded in the i-region of p-i-n diodes; we studied how the bias voltage Vb affects the normal photocurrentIgenerated by the visible light and a “two-step” photocurrent ΔIgenerated by the absorption of visible and infrared photons. We found that as Vb exceeds −0.2 V, ΔI rises and peaks at 0.6 V, while the normal photocurrentI falls to about half of its saturated level. These findings are discussed in terms of a rate equation model to show that ΔI is mainly determined by the balance of escape and recombination of photogenerated carriers.