Mechanically Stacked GaAs/GaInAsP Dual-Junction Solar Cell with High Conversion Efficiency of More than 31%

Abstract

We successfully fabricated high-performance GaAs and GaInAsP (band gap = 0.95 eV) single-junction solar cells with an area of 1×1 cm2. The conversion efficiencies of the GaAs and GaInAsP cells were 25.0 and 19.3%, respectively, under 1-sun air-mass 1.5 global (AM1.5G) conditions. The GaInAsP cell as the bottom cell under the mechanically stacked GaAs top cell also showed a high efficiency of 6.1%, and a total efficiency of 31.1% was achieved for the GaAs/GaInAsP tandem cell. This is the highest efficiency obtained under 1-sun AM1.5G conditions among the dual-junction cells ever reported.

Semiconductor Wafer Bonding for Solar Cell Applications: A Review

“…Prior to the development of wafer bonding, simple stacking of two cells on top of each other with a spacing frame, so-called mechanical stacking, was used to fabricate four-terminal multijunction solar cells, as a simple strategy to circumvent the lattice-mismatching problem in heteroepitaxial growth (Figure 3). [147][148][149][150] This technique offers advantages such as freedom from current-matching conditions and electrical resistance at the tunneling junction in heteroepitaxy or the bonded heterointerface. In contrast, this approach suffers from drawbacks such as optical loss due to the refractive-index mismatch between the semiconductors and the air gap, as well as difficulties in using image.…”

“…[112,113] the electrical output from independent subcells. Nonetheless, in four-terminal configurations, high total energy conversion efficiencies were achieved, including 31.1%, 32.6%, and 33.3% for mechanically stacked GaAs/InGaAsP, [150] GaAs/GaSb, [147] and InGaP/ GaAs/InGaAs [148] dual-and triple-junction cells, respectively.…”

“…In contrast, this approach suffers from drawbacks such as optical loss due to the refractive‐index mismatch between the semiconductors and the air gap, as well as difficulties in using the electrical output from independent subcells. Nonetheless, in four‐terminal configurations, high total energy conversion efficiencies were achieved, including 31.1%, 32.6%, and 33.3% for mechanically stacked GaAs/InGaAsP, [ 150 ] GaAs/GaSb, [ 147 ] and InGaP/GaAs/InGaAs [ 148 ] dual‐ and triple‐junction cells, respectively.…”

Adhesive bonding for mechanically stacked solar cells

“…The top cell specification was fixed as a seriesconnected dual-junction tandem cell with 1.85 (GaInP) and 1.42 (GaAs) eV junctions, while the bandgap of a Selected results for the efficiency of multi-junction cells over the past decade. Additional references not in text: [12][13][14][15].…”

“…Selected results for the efficiency of multi‐junction cells over the past decade. Additional references not in text: .…”