Fabrication of High-Efficiency III–V on Silicon Multijunction Solar Cells by Direct Metal Interconnect

Abstract

This paper presents a novel direct-metal-interconnect hybrid integration method for the fabrication of low cost and highefficiency multijunction solar cells without being constrained by lattice matching requirements. It also incorporates the areal current matching technique that is essential in mitigating the adverse effects of current limiting by the Si subcell to achieve maximum possible efficiency. A GaInP/InGaAs/Si triple-junction solar cell has been demonstrated, with a 2-terminal estimated efficiency of 25.5% tested under a filtered Xe arc lamp with the light intensity set to 100 mW/cm 2 . The cell shows promising thermal reliability, as well as potential for operation under concentrated illumination.Index Terms-Current matching, III-V on Si, multijunction (MJ) solar cell, photovoltaic (PV), solar spectrum.

III–V Multijunction Solar Cell Integration with Silicon: Present Status, Challenges and Future Outlook

“…Si being an indirect bandgap semiconductor typically limits the overall current when integrated in tandem with conventional 2J InGaP/GaAs solar cells in 3J twoterminal configuration (Derendorf et al 2013;Yang et al 2014;Garcia-Tabares et al 2011). Hence, the design of bottom Si subcell is extremely important for current-matching in tandem cell design.…”

“…DMI technique is capable of providing high tolerance to disparate materials with difference in lattice constants and thermal expansion coefficients, allowing for greater freedom in choosing the subcell materials with optimal bandgap combinations. Yang et al (2014) demonstrated a 3J GaInP/GaAs/Si solar cell using the DMI approach. The 2J GaInP/GaAs cells were first grown on lattice-matched Ge substrate, thereafter the substrate was removed using epitaxial lift-off technique, and the metallized front side of the 2J cell was attached to a transparent quartz wafer for support.…”

“…With a bandgap of 1.12 eV, Si substrate is a better bottom cell candidate in comparison to Ge substrate (bandgap -0.67 eV) for integration with standard dual-junction (2J) InGaP/GaAs based multijunction solar cells in regard to current-matching (Derendorf et al 2013). Such triple-junction (3J) InGaP/GaAs//Si solar cells (monolithically or mechanically stacked) are likely to be the quickest path for high-efficiency III-V-on-Si solar cells (Green 2014) with theoretically efficiency in excess of 40% at AM1.5g and AM1.5d (Derendorf et al 2013;Yang et al 2014). A recent study has revealed that transitioning from a 4" Ge substrate to a 8" Si substrate would correlate to about 60% reduction in cost for multijunction solar cells (D'Souza et al 2011).…”

High-resolution X-ray diffraction and micro-Raman scattering studies of Ge(:Ga) thin films grown on GaAs (001) substrates by MOCVD

“…Recent developments in tandem solar cells and broadband photodetectors have caused an increasing research interest in materials integration between group-IV and III-V semiconductors. 1,2 Monolithic growth of Ge-on-GaAs and/or GaAs-on-Ge has thus been a natural focus for band broadening because of the small lattice mismatch ($0.083%) between Ge and GaAs. Unfortunately, atomic interdiffusions across the grown interface during the overgrowth caused by the 'selfannealing' effect pose a great challenge, 3,4 beside the polar/ nonpolar mismatch problem when growing GaAs-on-Ge, 5 for materials integration of Ge and GaAs by any epitaxial growth method.…”

Structural properties of In0.53Ga0.47As epitaxial films grown on Si (111) substrates by molecular beam epitaxy

“…And the heteroepitaxial growth of In x Ga 1 − x As films on Si substrates are expected to be used for the fabrication of high-efficiency solar cells [6,7], laser diodes [8,9], photodetectors [10,11], and so on. In particular, the In x Ga 1 − x As with high In composition of 0.53 is a promising candidate III-V compound semiconductor for a metal-oxide-semiconductor field-effect transistor (MOSFET) channel material due to its high electronic mobility and high breakdown field [12,13].…”