Achieving 27.7% Efficiency with a Mechanically Stacked, Four-Terminal Perovskite/InGaAsP Tandem Solar Cell

Multijunction solar cell architectures offer a means to exceed the efficiency limits of traditional single-junction cells, notably surpassing the Shockley-Queisser limit. III-V compound semiconductors, known for their adaptable bandgaps, are often used in constructing multijunction cells, but their fabrication largely relies on complex epitaxial growth techniques. These processes are further complicated by the demanding necessity for lattice-matched, heavily-doped tunnel junctions. To address these challenges, our study introduces a mechanically stacked, four-terminal perovskite/InGaAsP tandem solar cell as a viable alternative to conventional all-III-V semiconductor dual-junction cells. We successfully achieved a low-bandgap InGaAsP solar cell with an impressive efficiency of 19.0% and an open-circuit voltage of 657 mV by employing carrier-selective contacts, a performance that rivals state-of-the-art InGaAsP homojunction solar cells. Furthermore, by pairing an InGaAsP bottom cell with a semi-transparent perovskite top cell in a tandem configuration, we attained a remarkable efficiency of 27.7% along with an outstanding open-circuit voltage of 1.7 V. The remarkable proof-of-concept demonstration presented here not only paves the way for highly efficient dual-junction thin film flexible solar cells but also simplifies the fabrication process by eliminating the need for lattice-matched tunnel junction layers, a common requirement in conventional III-V multijunction solar cells.