This paper investigates the possibility of increasing the spectral sensitivity of an organic-inorganic p-i-n-heterostructure solar cell as compared to a p-n-structure solar cell. Both p-i-n and p-n structures are fabricated from gallium arsenide (GaAs) and copper phthalocyanine (CuPc) using the same technology. In fabricating the p-n-structure, CuPc is deposited in a thinner layer and is fully doped with oxygen; in fabricating the p-i-n-structure, CuPc is deposited in a thicker layer and only its upper part is doped. The main properties of both heterostructures are investigated. The shift in spectral absorption maximum towards the shorter wavelength portion of the spectrum is found to increase the spectral sensitivity and efficiency of the p-i-n-heterostructure n-GaAs/(i-CuPc)/p-CuPc compared to the p-n-heterostructure n-GaAs/p-CuPc. The discussed technology can be used to optimize the solar cell performance under the low temperature and cloud cover conditions.