Tailoring Light Management in All‐Perovskite Tandem Solar Cells: The Impact of Nanotextures

All‐perovskite tandem solar cells (APTSCs) emerge as promising low‐cost and high‐efficiency next‐generation photovoltaics. To further increase the power conversion efficiencies (PCEs), a deeper understanding and fine‐tuned optimization of the optics is required, since most reports fall below 90% of the theoretical limit in photocurrent. Here, we demonstrate a synergistic multi‐faceted approach to overcome the optical constraints: incorporation of front‐sided nanotextures into APTSCs yields a broadband improvement of light in‐coupling, which eliminates thin‐film interference effects in reflectance, equivalent to a gain of 0.45 mA∙cm −2 in photocurrent. On the material level, parasitic absorption is reduced by optimizing the front ITO layer and replacing PEDOT:PSS for the bottom subcell with a graphene oxide/self‐assembled monolayer (GO/SAM) bilayer, improving the overall current gain to 1 mA∙cm −2 in each subcell. The resulting APTSC achieves a power conversion efficiency (PCE) of 27.98% with a short‐circuit current density ( J SC ) of 17.18 mA∙cm −2 , one of the highest reported values for this technology to date. Through comprehensive optical simulations, we explore the optical potential of APTSCs and further highlight upper limits of the subcell photocurrents in various tandem architectures. This work provides experimental and theoretical insights into optical optimization routes to increase the PCE of APTSCs well beyond 30%.