Snaith group

Abstract:

ABSTRACT Narrow‐bandgap tin and mixed tin–lead halide perovskites are attracting growing interest for optoelectronic applications, yet the difficult‐to‐control crystallization process has hindered their development. Although additive engineering has effectively improved film formation, the fundamental origins of their distinct crystallization behavior remain less explored. Here, through direct comparison with Pb counterparts, we investigate the pre‐crystallization stages of Sn‐based perovskite precursor solutions through complementary structural characterizations. We show that Sn precursors are intrinsically more reactive and sensitive to their chemical environment, exhibiting poorer colloidal stability compared to Pb and a strong inherent tendency to agglomerate. These findings explain their narrower processing window, where small variations in solution chemistry strongly affect nucleation and crystallization dynamics. To fabricate high‐quality tin‐based perovskite through solution methods, we highlight the importance of controlling the often‐overlooked pre‐crystallization stages, though, for example, rational solvent and additive designs. Overall, we provide fundamental insights into precursor solution chemistry and establish pre‐crystallization engineering as a key strategy for overcoming long‐standing limitations in thin‐film fabrication, particularly in light of the field's rapid progression toward large‐scale, sustainable, and solvent‐conscious manufacturing.

Abstract:

Narrow-bandgap tin and mixed tin-lead halide perovskites are attracting growing interest for optoelectronic applications, yet the difficult-to-control crystallization process has hindered their development. Although additive engineering has effectively improved film formation, the fundamental origins of their distinct crystallization behavior remain less explored. Here, through direct comparison with Pb counterparts, we investigate the pre-crystallization stages of Sn-based perovskite precursor solutions through complementary structural characterizations. We show that Sn precursors are intrinsically more reactive and sensitive to their chemical environment, exhibiting poorer colloidal stability compared to Pb and a strong inherent tendency to agglomerate. These findings explain their narrower processing window, where small variations in solution chemistry strongly affect nucleation and crystallization dynamics. To fabricate high-quality tin-based perovskite through solution methods, we highlight the importance of controlling the often-overlooked pre-crystallization stages, though, for example, rational solvent and additive designs. Overall, we provide fundamental insights into precursor solution chemistry and establish pre-crystallization engineering as a key strategy for overcoming long-standing limitations in thin-film fabrication, particularly in light of the field's rapid progression toward large-scale, sustainable, and solvent-conscious manufacturing.

Abstract:

Vacuum-based deposition is a scalable, solvent-free industrial method ideal for uniform coatings on complex substrates. However, all vacuum-deposited perovskite solar cells fabricated by thermal evaporation trail solution-processed counterparts in efficiency and stability due to film quality challenges, necessitating advancement and improved understanding. Here, we report a co-evaporation route for 1.67-eV wide-bandgap perovskites by introducing a PbCl2 co-source to optimize film quality. We promote perovskite formation with pronounced (100) “face-up” orientation and deliver a certified all vacuum-deposited solar cell with 18.35% efficiency (19.3% in the lab) for 0.25-cm2 devices (18.5% for 1-cm2 cells). These cells retain 80% of peak efficiency after 1,080 hours under the ISOS-L-2 protocol. Leveraging operando hyperspectral imaging, we provide spatiotemporal spectral insight into halide segregation and trap-mediated recombination, correlating microscopic luminescence features with macroscopic device performance while distinguishing radiative from non-ideal recombination channels. We further demonstrate 27.2%-efficient 1-cm2 evaporated perovskite-on-silicon tandems and outdoor stability of all vacuum-deposited tandems in Italy, retaining ~80% initial performance after 8 months.

Abstract:

Raw data for 'Homogenized optoelectronic properties in perovskites: achieving high-efficiency solar cells with common chloride additives'

Abstract:

The anisotropy of perovskite nanoplatelets (PeNPLs) opens up many opportunities in optoelectronics, including enabling the emission of linearly polarized light. But the limited stability of PeNPLs is a pressing challenge, especially for red-emitting CsPbI3. Herein, we address this limitation by alloying formamidinium (FA) into the perovskite cuboctahedral site. Unlike Cs/FA alloying in bulk thin films or nanocubes, FA incorporation in nanoplatelets requires meticulous control over the reaction conditions, given that nanoplatelets are obtained in kinetically-driven growth regimes instead of thermodynamically-driven conditions. Through in-situ photoluminescence (PL) measurements, we find that excess FA leads to uncontrolled growth, where phase impurities and nanoplatelets of multiple thicknesses co-exist. Restricting the FA content to up to 25% Cs substitution enables monodisperse PeNPLs, and increases the PL quantum yield (from 53% to 61%), exciton lifetime (from 18 ns to 27 ns), and stability in ambient air (from ~2 days to >7 days) compared to CsPbI3. This arises due to hydrogen bonding between FA and the oleate and oleylammonium ligands, anchoring them to the surface to improve optoelectronic properties and stability. The reduction in non-radiative recombination, improvement in the nanoplatelet aspect ratio, and higher ligand density lead to FA-containing PeNPLs more effectively forming edge-up superlattices, enhancing the PL degree of linear polarization from 5.1% (CsPbI3) to 9.4% (Cs0.75FA0.25PbI3). These fundamental insights show how the stability limitations of PeNPLs could be addressed, and these materials grown more precisely to improve their performance as polarized light emitters, critical for utilizing them in next-generation display, bioimaging, and communications applications.