Photovoltaic spectra of a GaAs/Al_(0.35)Ga_(0.65)As/GaAS (50(?)/40(?)/100(?)) asymmetric coupled quantum well P-I-N structure at room temperature are reported for the first time. The photovoltaic spectra clearly show the "step-like" shape and distinct excitonic peaks from the two quantum wells. The energy positions of these excitonic peaks are in agreement with that of the photocurrent and photoluminescence spectra. In addition, the polarization of the heavy-and light-holes excitonic transitions in the photovoltaic spectra has been observed. The mechanism yielding photovoltaic spectra is discussed in the paper.