Promoted monolithic perovskite/organic tandem solar cells through elaborate manipulation of light transmission and carrier tunneling in interconnect junction

Monolithic perovskite/organic tandem solar cells (TSCs) have emerged as promising thin film solar cells. It is recognized that interconnect junction plays a pivotal role in tandem devices. Consequently, wide bandgap Cs_0.25FA_0.75Pb(I_0.6Br_0.4)₃ perovskite top-cell and narrow bandgap PM6:Y6:PC₆₁BM ternary organic bottom-cell were integrated in this study with several kinds of thin metal interconnect layers, which provides feasibility to elaborately manipulate light transmission and carrier tunneling process in interconnect junction. It is confirmed that, in comparison with Au, employing an Ag interconnect layer elevates integrated transmittance of light in longer wavelength regions, mainly because of the alleviated screening effect with a lower free electron concentration, which offers sufficient light harvest for the bottom-cell. Meanwhile, established energy barriers with moderate height afford convenient extraction and recombination for both holes and electrons. Hence, the performance of TSCs is promoted substantially. Moreover, an innovative Ag/Au double interconnect layer is proposed accordingly, which can preserve exceptional conductivity and light transmission and further reduce barrier height, especially for hole tunneling, by optimizing the band alignment between the interconnect layer and bottom-cell. Resultantly, the monolithic perovskite/organic TSC with a striking efficiency of 23.26% is achieved. In a word, this study can pave a general approach toward high-performance TSCs integration.