Xiaojing Ci

Unbalanced crystallization kinetics in mixed Sn‐Pb perovskite cause film heterogeneity and high defect densities, thereby constraining overall performance and stability, particularly under scalable processing conditions. Here, we investigate nanocrystal‐mediated crystallization regulation in ambient‐processed, slot‐die‐coated narrow‐bandgap Sn‐Pb perovskites by combining CsPbI ₃ nanocrystal‐assisted processing with time‐resolved in situ grazing‐incidence wide‐angle X‐ray scattering (GIWAXS). After nine ISOS‐T‐3 thermal cycles, the perovskite solar cells (PSCs) fabricated from seeded perovskite films retain 80% of their initial efficiency at 25°C. Operando GIWAXS reveals differences in lattice evolution, residual PbI ₂ formation, and microstrain accumulation between the control and nanocrystal‐assisted films. By linking scalable processing and crystallization kinetics to the subsequent lattice response under thermal cycling, this work establishes a processing, crystallization, structure, stability relationship for narrow‐bandgap Sn‐Pb perovskites and highlights the importance of controlling early‐stage film formation for thermally robust, scalable perovskite photovoltaics.

Optoelectronic performance, defect density, and thin-film morphology of solution-processable lead halide perovskites are highly dependent on nucleation and growth conditions during processing. Additionally, Cs+ incorporation into the lattice can have benign effects on the thin films, which is challenging for scalable, deposition-friendly solvents such as 2-methoxyethanol or acetonitrile due to their highly limited solubility of Cs-containing salts. To address both issues, we present an interface-engineering approach that utilizes CsPbI3 nanocubes as seed crystals for slot-die coating of FAPbI3. The seeds improve growth-control at the bottom interface and enhance Cs+ incorporation into the active layer lattice. Incidence angle varied grazing-incidence wide-angle X-ray scattering enables depth-resolved structural probing of thin films, revealing increased Cs+ incorporation with increasing film depth. Additionally, morphological parameters, such as thin-film “face-on” orientation and crystallographic texture, are significantly improved in the seeded film. Accordingly, the seeded films exhibit reduced defect density and enhanced charge-carrier separation due to increased structural ordering and Cs+ alloy-induced bandgap tuning across the active layer thickness. Resulting p-i-n photovoltaic devices exhibit superior mean values as well as a narrower spread across short-circuit current density, fill factor, and power conversion efficiency, highlighting the beneficial effects of nanocrystal seeding on active-layer quality and reproducibility.

Wide-bandgap perovskite solar cells play a key role in tandem solar cells, which aim to overcome the Shockley-Queisser limit for single-junction solar cells. In this work, we develop and optimize a gas quenching method under ambient conditions for the fabrication of wide-bandgap (1.77 eV) perovskite films. To improve the performance of PSCs, three different organic spacer cations, including aromatic amino molecules (PEAI), aliphatic amino with long alkyl chain molecules (OAI), and short alkyl chain molecules (BAI), are applied and investigated as surface passivation materials. As a result, the 2D perovskite layers form on top of the 3D perovskite films. The n-i-p devices with PEAI passivation exhibit the highest photovoltaic performance with a champion power conversion efficiency (PCE) of 16.26% along with a high V_oc of 1.21 V, exceeding the control device (PCE = 13.42%, V_oc = 1.15 V), and maintaining 88% of its initial PCE after 120 min of continuous illumination under a nitrogen atmosphere at room temperature. This work offers a guide for the fabrication of wide-bandgap PSCs under ambient conditions and the choice of organic spacer cations for passivation.