Synergetic substrate and additive engineering for over 30%-efficient perovskite-Si tandem solar cells

Perovskite-silicon (Si) tandem solar cells are the most prominent contenders to succeed single-junction Si cells that dominate the market today. Yet, to justify the added cost of inserting a perovskite cell on top of Si, these devices should first exhibit sufficiently high power conversion efficiencies (PCEs). Here, we present two key developments with a synergetic effect that boost the PCEs of our tandem devices with front-side flat Si wafers—the use of 2,3,4,5,6-pentafluorobenzylphosphonic acid (pFBPA) in the perovskite precursor ink that suppresses recombination near the perovskite/C₆₀ interface and the use of SiO₂ nanoparticles under the perovskite film that suppresses the enhanced number of pinholes and shunts introduced by pFBPA, while also allowing reliable use of Me-4PACz as a hole transport layer. Integrating these developments in an optically and electrically optimized tandem device (e.g., with a durable Si cell), reproducible PCEs of 30 ± 1%, and a certified maximum of 30.9% are achieved.