We have investigated tandem devices based on III-V and IV semiconductor materials for the top and bottom sub-cells such as InGaAs(P)/InP, GaAs/Ge, AlGaAs/Si and Si/Ge assembled with three terminals and operated independently. The two sub-cells are connected back to back and separated by a middle common contact. Compared with two terminals, three terminals avoid the loss due to current mismatching between the sub-cells, and the resistance loss originating from the tunnel junction between the sub-cells.

We have undertaken a comprehensive modeling and simulation for device design, optimization and performance prediction of these tandem cells. Optimal current-voltage and power-voltage characteristics were generated for individual cells together with the corresponding quantum efficiency spectra. The predictions show that an extended spectral coverage is achieved leading to an enhanced overall performance of these tandem devices.

The potential applications of these devices in PV and concentrator PV (CPV) were assessed and the output parameters were predicted as a function of the simulated concentration ratio of the incident light under AM1.5 illumination conditions. TPV applications were also investigated as some of the materials used (like InGaAs and Ge) are sensitive to the near infrared. Because temperature is critical for device operation under CPV and TPV especially in this part of the world, the effect of the operating temperature on the overall efficiency was also simulated and discussed.


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  • Received: 05 February 2012
  • Accepted: 22 March 2012
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