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2D Ruddlesden–Popper perovskites have risen to prominence as stable and efficient photovoltaic materials because of their structural diversity, rich photophysics, and low moisture ingression. However, thin films processed from stoichiometric precursor solutions possess a broad phase distribution of different number of inorganic layers with random crystal orientation, crippling device performance. The effect of methylammonium chloride (MACl) and 3‐amino‐4‐phenolsulfonic acid (APSA) on the fabrication of perpendicularly oriented (PEA)2MA4Pb5I16films with narrow phase distribution using antisolvent and hot‐casting processing techniques is investigated. MACl plays a critical role in suppressing parasiticn ≤ 2 and 3D‐like phases. APSA performs the dual function of trap passivation and further narrowing phase polydispersity through strong coordination with Pb2+. Ex situ grazing‐incident wide‐angle X‐Ray scattering (GIWAXS) and ultrafast spectroscopic characterization reveal uniformly mixed‐phase distribution with disordered orientation in antisolvent treated films, while additive‐assisted hot‐casting treatment results in oriented, reverse‐graded phase distribution, i.e., small‐non the film surface and large‐nat the bottom. Arising thin films enable efficient p–i–n solar cells with an efficiency of 14.34%, and aVocof 1.20 V, retaining 96% initial efficiency after 1440 h under ambient conditions (RH = 50–60%) without encapsulation.
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Revealing the Crystallization Pathways of Mixed‐Halide Low‐Dimensional Perovskites: A First Step Toward Solar Cell Applications
Ruddlesden–Popper perovskites (RPPs) are promising materials for optoelectronic devices. While iodide‐based RPPs are well‐studied, the crystallization of mixed‐halide RPPs remains less explored. Understanding the factors affecting their formation and crystallization are vital for optimizing morphology, phase purity, and orientation, which directly impact device performance. Here, we investigate the crystallization and properties of mixed‐halide RPPs (PEA)2FAn−1Pbn(Br1/3I2/3)3n + 1(PEA = C6H5(CH2)2NH3+and FA = CH(NH2)2+) (n = 1, 5, 10) using DMSO ((CH3)2SO) or NMP (OC4H6NCH3) as cosolvents and MACl (MA = CH3NH3+) as an additive. For the first time, the presence of planar defects in RPPs is directly observed by in situ grazing‐incidence wide‐angle X‐ray scattering (GIWAXS) and confirmed through the simulation of the patterns that matched the experimental. GIWAXS data also reveals that DMSO promotes higher crystallinity and vertical orientation, while MACl enhances crystal quality but increases halide segregation, shown here by nano X‐ray fluorescence (nano‐XRF) experiments. For low‐n RPPs, orientation is crucial for solar cell efficiency, but its impact decreases with increasing n. Our findings provide insights into optimizing mixed‐halide RPPs, guiding strategies to improve crystallization, phase control, and orientation for better performance not only in solar cells but also in other potential optoelectronic devices.
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- Award ID(s):
- 2324190
- PAR ID:
- 10618123
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Solar RRL
- Volume:
- 9
- Issue:
- 14
- ISSN:
- 2367-198X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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