BGaInAs solar cells lattice-matched to GaAs

The authors have recently demonstrated the epitaxial growth of B _xGa_1-x-yIn_yAs on GaAs substrates by metal-organic chemical vapor deposition. This new material has a bandgap less than that of GaAs, and can be grown lattice-matched to GaAs. Such a material, used as the second or third junction in a strain-free multijunction III-V solar cell, has the potential to increase the total cell efficiency. They report here on the performance of single-junction solar cells with 1.36-eV carbon- and silicon-doped B_0.03Ga _0.91In_0.06As bases and compare them with similar GaAs and Ga_0.94In_0.06As cells. The BGaInAs cells have exhibited less-than-ideal open-circuit voltages (V_oc and fill factors) (FF) of 0.57-0.66 V and 69%-73%, respectively. Poor red response of the quantum efficiencies and low short-circuit currents (j _sc) of 10-14 mA/cm² under AM1.5D conditions indicate that the minority-carrier diffusion lengths are short (<0.1 μm). The n-on-p devices perform slightly better than the p-on-n devices