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.