High-performance perovskite/Cu(In,Ga)Se2 monolithic tandem solar cells

Perovskite/CIGS tandem cellsTandem solar cells can boost efficiency by using more of the available solar spectrum. Han et al. fabricated a two-terminal tandem cell with an inorganicorganic hybrid perovskite top layer and a Cu(In,Ga)Se2 (CIGS) bottom layer. Control of the roughness of the CIGS surface and the use of a heavily doped organic hole transport layer were crucial to achieve a 22.4% power conversion efficiency. The unencapsulated tandem cells maintained almost 90% of their efficiency after 500 hours of operation under ambient conditions.Science, this issue p. 904The combination of hybrid perovskite and Cu(In,Ga)Se2 (CIGS) has the potential for realizing high-efficiency thin-film tandem solar cells because of the complementary tunable bandgaps and excellent photovoltaic properties of these materials. In tandem solar device architectures, the interconnecting layer plays a critical role in determining the overall cell performance, requiring both an effective electrical connection and high optical transparency. We used nanoscale interface engineering of the CIGS surface and a heavily doped poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) hole transport layer between the subcells that preserves open-circuit voltage and enhances both the fill factor and short-circuit current. A monolithic perovskite/CIGS tandem solar cell achieved a 22.43% efficiency, and unencapsulated devices under ambient conditions maintained 88% of their initial efficiency after 500 hours of aging under continuous 1-sun illumination.