Monolithic Bifacial Perovskite-CdSeTe Tandem Solar Cells

Monolithic metal halide perovskite-cadmium selenide telluride (CdSeTe) tandem thin-film solar cells have not been demonstrated to date, primarily due to the challenge of the almost-fixed architecture of CdSeTe cells that is incompatible with conventional tandem designs. Here, we report a monolithic bifacial thin-film tandem design that not only enables monolithic integration of perovskite-CdSeTe tandems but also delivers a high equivalent power conversion efficiency by harvesting the albedo light. The bifacial design allows better current match and thus enables higher total power output density of the tandem devices than conventional tandem cells. Using our innovative bifacial tandem design strategy, we have fabricated proof-of-concept monolithic bifacial perovskite-CST tandem solar cells with a stabilized power output of 23 mW/cm(2) and a bifacial equivalent efficiency of 23% under bifacial illumination with 1-sun front illumination and an albedo of 0.4.