Highly Efficient and Cost-Effective

Triple-junction solar cells made of III-V semiconductors and silicon have the potential to take photovoltaics to a new level of efficiency.

III-V Silicon Tandem Photovoltaics

III-V tandem solar cells can absorb light across a broad range of wavelengths in the solar spectrum and are ideally suited to efficiently convert UV, visible and near infrared photons into electricity.  In combination with silicon as a bottom cell, highly efficient tandem solar cells with two or even three sub-cells can be realized. The III-V sub-cells are only a few micrometers thick, due to the high absorption properties of the III-V compound semiconductor materials. This combination of materials opens up interesting ways for a cost-effective production, however, there are still challenges to be met, which we are addressing in our ongoing R&D projects: One challenge is to develop a cost-effective epitaxial growth of III-V layers on silicon, i.e. to overcome the lattice constant differences in the various materials. Currently we are investigating two concepts for 2-terminal monolithic solar cells. On the one hand, the III-V layers are grown directly on silicon, and on the other hand, they are transferred from a GaAs to Si substrate using wafer or adhesive bonding. At Fraunhofer ISE we achieved a peak conversion efficiency of 34.5% (AM 1.5g) for a III-V silicon tandem solar cell, thus establishing a new world record.

Highlights

  • GaInP/GaInAsP//Si triple-junction solar cell achieves record efficiency of 35.9% (AM1.5g) through improved mid-cell material (Press Release)
  • GaInP/AlGaAs//Si triple-junction solar cell (2-terminal) with record efficiency of 34.5% (AM1.5g) (Press Release | Paper)
  • GaInP/GaAs/Si triple-junction solar cell (2-terminal) produced by direct epitaxial growth on less costly silicon, achieves efficiencies up to 25.9% (AM1.5g) (Press Release)
  • GaAsP/Si tandem solar cells are developed for solar energy conversion and solar hydrogen production (See project websites for SiTaSol, DEPECOR and H2Demo)

Research & Development

We develop III-V silicon solar cells using direct epitaxy as well as by wafer bonding or adhesive bonding. All III-V semiconductor layers are manufactured in our two modern, industrial-scale MOVPE reactors: an AIX2800 G4 TM reactor with 8 x 6 inch configuration and a CRIUS showerhead reactor for 7 x 4 inch or 1 x 300 mm substrates. For the direct epitaxial growth, GaP is grown on silicon and then the lattice constant of GaAsP is tuned to produce absorbers with a band gap between 1.4 eV (GaAs) and 1.9 eV (GaInP). By varying the growth conditions in this process, we have been successful in reducing defect densities in recent years to ca. < 107 cm-2 for GaAs on silicon. Further challenges are the development of suitable absorber layers, barriers and tunnel diodes.

For the wafer-bonded structures, we first grow the upper III-V semiconductor layers on gallium arsenide and then transfer them to a partially processed silicon bottom cell. The connection can be realized by a direct wafer bond or a conductive adhesive bond. A two-terminal monolithic device is created. To reach our aim and lower costs, the cell production requires cost-effective production processes for i) the III-V layers, ii) the transfer of the thin layers of a few micrometers, iii) the bonding or adhesive technology and iv) the recycling of the expensive GaAs substrates. These are all important research aspects to which we are dedicated.

Our R&D Services

  • Direct epitaxy of III-V semiconductors on silicon with diameters up to 300 mm (Examples: GaP nucleation on silicon, GaPN, GaAsP, GaAs, GaInP)
  • Characterization of defects in III-V semiconductor layers (e.g. antiphase domains, stacking defects, mismatch dislocations)
  • Processing and process development for III-V devices on silicon bottom cells

Press Releases and News on this Research Topic:

 

Press Release

Higher and Faster with Tandem Photovoltaics – The Focus of Fraunhofer ISE at the EU PVSEC Conference

 

Press Release

New Record Efficiency for Tandem Solar Cell Technology

News

European researchers analyze environmental impact of new III-V/Si tandem solar cell technology – article in Energy & Environmental Science

Press Release

Fraunhofer ISE Sets Two Records for the Efficiency of Silicon-Based Monolithic Triple-Junction Solar Cells

Further Information on this Research Topic:

R&D Infrastructure

Center for High Efficiency Solar Cells

Research Project

PoTaSi

Demonstration of the Potential of Monolithic Tandem Solar Cells Made of III-V Semiconductors and Silicon

Research Topic

Silicon Bottom Cells for Tandem Photovoltaics

Research Project

SiTaSol

Application Relevant Validation of c-Si Based Tandem Solar Cell Processes with 30 % Efficiency Target

Current publications - III-V Silicon Tandem Photovoltaics:

YearTitle/AuthorDocument Type
202034.1 % Efficient GaInP/AlGaAs//Si Tandem Cell
Dimroth, F.; Schygulla, P.; Lackner, D.; Müller, R.; Benick, J.; Beutel, P.; Predan, F.; Höhn, O.; Hauser, H.; Siefer, G.; Hermle, M.; Glunz, S.
Conference Paper
2020Advances in Epitaxial GaInP/GaAs/Si Triple Junction Solar Cells
Feifel, M.; Lackner, D.; Ohlmann, J.; Volz, K.; Hannappel, T.; Benick, J.; Hermle, M.; Dimroth, F.
Conference Paper
2020Two-Terminal direct Wafer bonded GaInP/AlGaAs//Si Triple-Junction Solar Cell with AM1.5g Efficiency of 34.1 %
Lackner, D.; Höhn, O.; Müller, R.; Beutel, P.; Schygulla, P.; Hauser, H.; Predan, F.; Siefer, G.; Schachtner, M.; Schön, J.; Benick, J.; Hermle, M.; Dimroth, F.
Journal Article
2019Direct Growth of GaInP/GaAs/Si Triple-Junction Solar Cell with 22.3% AM1.5g efficiency
Feifel, Markus; Lackner, David; Ohlmann, Jens; Benick, Jan; Hermle, Martin; Dimroth, Frank
Journal Article
This publication list has been generated from the publication database Fraunhofer-Publica.