Memory Seeds Enable High Structural Phase Purity in 2D Perovskite Films for High‐Efficiency Devices

Abstract

Two-dimensional (2D) perovskites are a class of halide perovskites offering a pathway for realizing efficient and durable optoelectronic devices. However, the broad chemical phase space and lack of understanding of film formation have led to quasi-2D perovskite films with polydispersity in perovskite layer thicknesses, which have hindered devices performance and stability. Here, we demonstrate a scalable approach involving dissolution of single-phase crystalline powders with homogeneous perovskite layer thickness in desired solvents, to fabricate 2D perovskite thin-films with high phase purity. In-situ characterizations reveal the presence of sub-micron-sized seeds in solution that preserve the memory of the dissolved single-crystals and dictate the nucleation and growth of grains with identical thickness of the perovskite layers in thin-films. Photovoltaic devices fabricated with such films, yields an efficiency of 17.1% and 1.20V open-circuit voltage, while preserving 97.5% of their peakperformance after 800 hours under illumination without any external thermal management.

Facet orientation tailoring via 2D-seed- induced growth enables highly efficient and stable perovskite solar cells

“…The final 3D perovskite films were obtained after annealing at 150 C for 15 min. The grain size was found to be around 1.3 mm in the TDS sample due to the introduction of seed (Figure S5), [22][23][24][25][26][27] substantially larger than that of the control sample, which is desirable for better photoelectric properties. 23,24 Moreover, due to the hydrophobicity of the introduced seed crystal, [28][29][30][31][32] the water contact angle increases with the increase of seed concentration (Figure S6), in favor of the device stability on resisting humidity.…”

“…Interestingly, the undesired (111) facet orientation has disappeared in the TDS precursor film, and it can be reasonably inferred that the 2D seed begins to regulate the crystallization of the 3D perovskite in the nucleation stage, 16 consistent with previous reports. 19,27 The DJ phase perovskite was chosen as the seed because the diamine compounds with two amino groups at both ends can bond with 4À octahedron at two sides, 35,36 which is more likely to provide nucleation sites for the highly oriented growth of 3D perovskite (Note S3; Figure S11).…”

Synthesis, Structure, and Tunability of Zero-Dimensional Organic–Inorganic Metal Halides Utilizing the m-Xylylenediammonium Cation: MXD2PbI6, MXDBiI5, and MXD3Bi2Br12·2H2O

“… 8 Very recently, the “Memory Seed Effect” has been reported, which involves dissolving presynthesized crystals in solvents such as DMF, which enables the preparation of high-quality thin films for a variety of layered perovskites. 9 The solutions have been shown to retain “memory seed” crystallites, which facilitates the production of phase-pure layered perovskites. 9 The use of this “Memory Seed Effect” has led to solar cells with power conversion efficiencies of 17.1% for (C 4 H 9 NH 3 ) 2 (CH 3 NH 3 ) 3 Pb 4 I 13 .…”

“… 9 The use of this “Memory Seed Effect” has led to solar cells with power conversion efficiencies of 17.1% for (C 4 H 9 NH 3 ) 2 (CH 3 NH 3 ) 3 Pb 4 I 13 . 9 …”

Deterministic fabrication of 3D/2D perovskite bilayer stacks for durable and efficient solar cells

“…We created a stable dispersion of 2D perovskite seed solution by dissolving the parent crystal powders in MeCN (fig. S5 and supplementary text) ( 26 , 27 ). In general, other than the solvents with Gutmann number 5 < D N < 18 kcal/mol, any Pb 2+ -weakly coordinating solvents such as DMF, GBL, and DMAc compared with DMSO can produce a dispersion of 2D perovskite seed solution.…”