Mechanically Stacked Four-Junction Concentrator Solar Cells

Myles A. Steiner, John F. Geisz, J. Scott Ward, Ivan Garcia, Daniel J. Friedman, Richard R. King, Philip T. Chiu, Ryan M. France, Anna Duda, Waldo J. Olavarria, Michelle Young, Sarah R. Kurtz

Research output: Contribution to conferencePaperpeer-review

2 Scopus Citations

Abstract

Multijunction solar cells can be fabricated by bonding together component cells that are grown separately. Because the component cells are each grown lattice-matched to suitable substrates, this technique allows alloys of different lattice constants to be combined without the structural defects introduced when using metamorphic buffers. Here we present results on the fabrication and performance of four-junction mechanical stacks composed of GaInP/GaAs and GaInAsP/GaInAs tandems, grown on GaAs and InP substrates, respectively. The two tandems were bonded together with a low-index, transparent epoxy that acts as an omni-directional reflector to the GaAs bandedge luminescence, while simultaneously transmitting nearly all of the sub-bandgap light. As determined by electroluminescence measurements and optical modeling, the GaAs subcell demonstrates a higher internal radiative limit and thus higher subcell voltage, compared with GaAs subcells without enhanced internal optics; all four subcells exhibit excellent material quality. The device was fabricated with four contact terminals so that each tandem can be operated at its maximum power point, which raises the cumulative efficiency and decreases spectral sensitivity. Efficiencies exceeding 38% at one-sun have been demonstrated. Eliminating the series resistance is the key challenge for the concentrator cells. We will discuss the performance of one-sun and concentrator versions of the device, and compare the results to recently fabricated monolithic four-junction cells.

Original languageAmerican English
Number of pages3
DOIs
StatePublished - 14 Dec 2015
Event42nd IEEE Photovoltaic Specialist Conference, PVSC 2015 - New Orleans, United States
Duration: 14 Jun 201519 Jun 2015

Conference

Conference42nd IEEE Photovoltaic Specialist Conference, PVSC 2015
Country/TerritoryUnited States
CityNew Orleans
Period14/06/1519/06/15

Bibliographical note

Publisher Copyright:
© 2015 IEEE.

NREL Publication Number

  • NREL/CP-5J00-63557

Keywords

  • III-V solar cell
  • Mechanical stack
  • Multijunction solar cell
  • Photon recycling

Fingerprint

Dive into the research topics of 'Mechanically Stacked Four-Junction Concentrator Solar Cells'. Together they form a unique fingerprint.

Cite this