Pre-Embedded Multisite Chiral Molecules Realize Bottom-Up Multilayer Manipulation toward Stable and Efficient Perovskite Solar Cells

The defects from functional layers and interface, the agglomeration of SnO₂ nanoparticles (NPs), and poor perovskite crystallization are the main barrier to further heightening the power conversion efficiency (PCE) and stability of regular perovskite solar cells. Here, a bottom-up multilayer manipulation strategy by pre-embedding multisite racemic DL-cysteine hydrochloride monohydrate (DLCH) into the SnO₂ electron transport layer (ETL) is reported. The positively and negatively charged defects from ETL, perovskite layer and their interface can be passivated through the synergistic effect of the ─SH, ─COOH, ─NH₃⁺, and Cl⁻ groups in DLCH. The synergy of multiple functional groups and multiple chemical bonds enables bottom-up cross-layer passivation, which minimizes bulk and interfacial nonradiative recombination losses. Furthermore, the multifunctional DLCH plays a role in inhibiting the agglomeration of SnO₂ NPs, managing photons, relieving interfacial tensile stress, and manipulating perovskite crystallization. Benefiting from the above advantages, the DLCH-incorporating device delivers a PCE of 24.01%, which is much higher than the 21.61% of the control device. Moreover, the DLCH-modified devices demonstrate inviting thermal and ambient stabilities by maintaining 93% of the initial efficiency after aging at 65 °C for 1800 h and 95% of the original PCE after aging under a relative humidity of 20–25% for 2000 h.