35.8% space and 38.8% terrestrial 5J direct bonded cells

Abstract

Spectrolab has fabricated a direct semiconductor bonded space solar cell with an efficiency of 3S.8% under the AMO space spectrum. Using a similar technology, Spectrolab has achieved as-junction (SJ) direct bonded terrestrial cell with a record efficiency of 38.8% under the one-sun AM1.SG terrestrial spectrum. Efforts to further improve the SJ cell efficiency have focused on development of the top 3 junctions (T3J) grown on GaAs. Experiments with top 3J isotype cells have yielded an improvement of 1 % in current and 100 mV in voltage for the T3J. Spectrolab has also made significant improvements in its direct bonding process. The improved process has increased bond strengths by more than a factor of S and eliminated issues with large voids.

Optically Enhanced Photon Recycling in Mechanically Stacked Multijunction Solar Cells

“…Because the mechanical stack involves a direct semiconductor bond, there is again no opportunity to enhance the photon recycling in the upper junctions. A similar wafer-bonded architecture was reported for a five-junction cell by Chiu et al [13], demonstrating a two-terminal 1-sun efficiency of 37.8%.…”

“…1, and additional ZnS intermediateindex dielectric films on either side of the epoxy maximize the transmission of normal-incidence subbandgap light. Mechanical stacks have several other attractive features and have recently been demonstrated in different forms by several groups [10]- [13]. Because the subcells are grown separately, the problems associated with lattice-mismatch [14] and thermal-expansion mismatch are nearly eliminated.…”

31% European InGaP/GaAs/InGaAs Solar Cells for Space Application

“…35.8% at AM0, has been demonstrated for a 5-junction cell fabricated by direct semiconductor bonding technique, i.e. not a monolithic process [1]. Using MBE, monolithic latticematched solar cells with efficiencies as high as 44% measured in concentrated sunlight have been demonstrated [2].…”

Artifact Interpretation of Spectral Response Measurements on Two‐Terminal Multijunction Solar Cells

“…[1] They hold the highest record efficiencies across different branches of solar-cell technologies. [2][3][4] Typically, multijunction solar cells are made in a two-terminal structure because of the simple workflow of device fabrication as well as the straightforward design of electrical terminals. The component subcells are electrically connected in series such that the device has only two terminals to interact with the external circuit.…”