Efficiency Enhancement Of Ingap/Ingaas/Ge Solar Cells With Gradually Doped P-N Junction Active Layers

Graded doping techniques have been studied to improve the power conversion efficiency of the InGaP/InGaAs/Ge solar cells. We have investigated the efficiency enhancement of the triple-junction solar cells with gradually doped p-n junction active layers. The triple-junction epi-structures are grown by metalorganic chemical vapor deposition on Ge (100) substrates. The photovoltaic devices are fabricated and characterized under AM1.5 global illuminations. It was found that the graded doping profiles in InGaP emitter and InGaAs base layers can contribute to the efficiency improvement of the InGaP/InGaAs/Ge solar cells. The open circuit voltage and the short circuit current were improved up to 3.7 and 1.3 %, respectively, by employing the graded doping technique.