27.6% efficiency (1 sun, air mass 1.5) monolithic Al0.37Ga0.63As/GaAs two-junction cascade solar cell with prismatic cover glass

Abstract

A 27.6% efficiency measured under 1 sun, air mass 1.5 illumination has been achieved in a two-terminal, monolithic two-junction cascade solar cell consisting of an Al0.37Ga0.63As (Eg=1.93 eV) upper cell and a GaAs lower cell. The component cells were electrically connected together using a metal-interconnect contact fabricated during post-growth processing. Also, a prismatic cover glass was bonded to the front surface of the cascade structure to minimize the obscuration effect introduced by the grid lines and metal-interconnect contacts. As the cascade cell was operated under air mass 0 illumination, an efficiency of 23.0% was obtained. Both results represent the highest 1 sun efficiencies ever reported. The implications of achieving this high efficiency in a two-junction cascade solar cell for terrestrial and space applications are also described.

III‐V Solar Cells

“…Much effort was invested in developing AlGaAs/GaAs double-junction solar cells ultimately resulting in an efficiency of 27.6% AM1.5G and 23.0% AM0 [90]; interestingly this solar cell did not use a tunnel junction, but rather a front metal interconnection scheme with shading losses mitigated by a prismatic lens. While AlGaAs yields a reasonable top cell, good-quality junctions require very clean precursors and careful control of the growth conditions [12,91].…”

The Outdoor Field Test of the 4T III-V on Si Tandem PV Module and Its Energy Yield Modeling

“…The principles of multi-junction cells were suggested in 1955 [7] and investigated in 1960 [8]. The significant progress was triggered by liquid-phase, and the vapor-phase epitaxy brought AlGaAs/GaAs multi-junction cells in the 1980s, with tunnel junctions [9] and metal interconnections [10][11][12]. At that moment, it was predicted that the power-conversion efficiency of multi-junction solar cells would reach close to 30% [13], but this was not achieved because of difficulties with high-performance, stable tunnel junctions [14] as well as oxygen-related defects in the AlGaAs at that time [15].…”

Organic photovoltaic materials and thin-film solar cells

“…Among all kinds of solar cells, inorganic semiconductors based solar cells have been developed very rapidly in the past decades and thus represent the most mature technology by taking up around 70% of photovoltaic markets nowadays. The silicon-based PVs have outstanding advantages in both efficiency and lifetime with power conversion efficiencies (PCE) in excess of 25% [1]. However, the high cost of raw materials and complicated processing techniques definitely limit their large-scale commercial developments.…”