28.28% of GaInP/sub 2//InGaAs/Ge triple-junction tandem cells

This paper reports our recent results of GaInP/sub 2//InGaAs/Ge triple-junction tandem solar cells produced by low-pressure (200 mbar) metal-organic vapor phase epitaxy (MOVPE). Our work focuses on the following improvements: (1) Developing the shallow p/n junction (less than 0.2 /spl mu/m) with high doping level (/spl sim/1/spl times/10/sup 19/cm/sup -3/) of Ge bottom cells and selecting GaInP/sub 2/ to be window layer. (2) Applying In/sub x/Ga/sub 1-x/As material as p/n junction of middle cells. (3) Adopting n/sup +/-n/sup -//p/sup -/-p/sup +/ configuration in GaInP/sub 2/ top cells. (4) Composing with wide band gap materials AlGaAs/GaAs or AIGaAs/GaInP/sub 2/ as the tunnel junctions. These modification can outstandingly advance our performance of produced GaInP/sub 2//InGaAs/Ge triple-junction tandem solar cells, which have reached 28.28% (AM0, 25/spl deg/C, 2/spl times/2 cm/sup 2/).