The-authors present preliminary data for a set of GaAsN/GaAs multiquantum well (MQW) solar cells, grown by radio-frequency (rf) nitrogen plasma-assisted chemical beam epitaxy. The spectral response of this preliminary set of devices extends well below the GaAs band gap, while exhibiting remarkably high photoconversion strength that exceeds that of other MQW-based solar cells with comparable band gaps (1.0-1.2 eV). This behavior is consistent with the enhancement of the electron effective mass in III-V dilute nitrides. Although the output current is similar to that of conventional GaInAsN solar cells, the output voltage is significantly higher when compared to that of bulk solar cells of similar wavelengths. The spectral response of as-grown devices is characterized by a deep valley around 1.37-1.4 eV, that could be attributed to N contamination of the GaAs barriers. Rapid thermal annealing improves significantly the spectral response in the vicinity of this valley. (c) 2007 American Vacuum Society.