Compensated Contacts for Three-Terminal Transistor Solar Cells

Mario Martinez, Simon Svatek, Marius Zehender, Myles Steiner, Emily Warren, Adele Tamboli, William McMahon, Ines Duran, Antionio Marti, Elisa Antolin

Research output: Contribution to conferencePaperpeer-review

1 Scopus Citations


The heterojunction bipolar transistor solar cell (HBTSC) is an alternative to conventional double-junction solar cells that combines the advantages of three-terminal architectures with a compact design. A critical part of the HBTSC fabrication is the implementation of the middle contact, the one associated to the base layer in the transistor structure, because this layer can be damaged by the diffusion of metallic species during contact annealing. As a solution we propose to implement a "compensated contact", that is, to leave a thin (< 200 nm) portion of emitter or collector between the base layer and the contact metals and compensate its doping during contact annealing. Using an Au/Zn/Au metal structure to compensate a 150 nm thick portion of the collector, we obtain a specific contact resistance 810-4 Ω cm2. This value is fairly invariant for annealing temperatures between 400 and 460°C and annealing times between 2 and 5 minutes, and it does not improve by adding Pd to the metallic stack. Optimizing the compensated contact technology opens the path to the realization of III-V-material-based HBTSCs with open-circuit voltages and fill factors comparable to those of conventional multijunction architectures.

Original languageAmerican English
Number of pages4
StatePublished - 20 Jun 2021
Event48th IEEE Photovoltaic Specialists Conference, PVSC 2021 - Fort Lauderdale, United States
Duration: 20 Jun 202125 Jun 2021


Conference48th IEEE Photovoltaic Specialists Conference, PVSC 2021
Country/TerritoryUnited States
CityFort Lauderdale

Bibliographical note

Publisher Copyright:
© 2021 IEEE.

NREL Publication Number

  • NREL/CP-5900-78983


  • heterojunction bipolar transistor solar cell
  • multijunction solar cell
  • specific contact resistance
  • transfer length method


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