InP-based tunnel junctions for ultra-high concentration photovoltaics.

To enhance the performance of multi-junction photovoltaics, we investigated three different InP-based tunnel junction designs: p++-InGaAs/n++-InP tunnel junction, p++-InGaAs/i-InGaAs-/n++-InP tunnel junction, and p++-InGaAs/i-InGaAs/n++-InGaAs tunnel junction. The p++-InGaAs/i-InGaAs/n++-InGaAs tunnel junction demonstrated a peak tunneling current density of 495 A/cm2 and a resistivity of 9.3 × 10-4 Ωcm2, allowing the tunnel junction device to operate at a concentration over 30000 suns. This was achieved by inserting an undoped InGaAs quantum well at the p++-InGaAs/n++InGaAs junction interfaces, which enhanced its stability within the operating temperature range of multi-junction solar cells. Moreover, the p++-InGaAs/i-InGaAs/n++-InGaAs tunnel junction exhibited the lowest resistance.