All-perovskite tandem solar cells (APTSCs) have emerged as a promising photovoltaic technology, with recent power conversion efficiencies (PCEs) exceeding 30%. However, their performance still lags behind that of perovskite/silicon tandems due to optical and electronic limitations. To bridge this gap, we present a comprehensive strategy addressing both light management and the reduction of non-radiative recombination losses.

The optical performance is enhanced by implementing advanced light management: Optimizing transparent conducting oxides (TCOs) enables precise tuning of thin-film interference, directing constructive interference toward the most beneficial spectral regions. Replacing the conventional PEDOT:PSS hole transport layer with self-assembled monolayers (SAMs) reduces parasitic absorption in the narrow-bandgap (NBG) subcell. Additionally, we introduce nanotextured surfaces, which significantly suppress reflection over a broad spectral range. These combined approaches increase the photogenerated current density by 1 mA/cm² in each subcell, achieving short-circuit current densities (JSC) above 17 mA/cm², which is among the highest reported for APTSCs.

To optimize the electronic quality, we focus on minimizing non-radiative recombination in the NBG subcell. Surface treatments at the perovskite–electron transport layer (ETL) interface in both wide-bandgap (WBG) and NBG subcells prove effective in reducing recombination losses. In the NBG subcell, replacing PEDOT:PSS with SAMs improves device stability and reduces parasitic absorption. However, we find that the use of thiocyanate-based additives like Pb(SCN)₂, while beneficial in PEDOT:PSS-based devices, hinders charge extraction in SAM-based architectures[1]. By optimizing SAM-substrate binding, we achieve improved interfacial properties and VOCs up to 0.88 V—surpassing the performance of PEDOT:PSS-based counterparts.

Furthermore, we investigate alternative materials for the recombination junction between subcells, demonstrating that a well-engineered transparent conductive oxide can significantly reduce voltage losses. The integration of these strategies results in champion PCEs >27% in all-perovskite double and triple junction solar cells[2]. These advances lay the foundation for future devices exceeding 30% efficiency, paving the way for high-performance, stable all-perovskite tandem solar cells.