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Castro-Méndez AF, Jahanbakhshi F, LaFollette DK, Lawrie BJ, Li R, Perini CAR, Rappe AM, Correa-Baena JP. Tailoring Interface Energies via Phosphonic Acids to Grow and Stabilize Cubic FAPbI 3 Deposited by Thermal Evaporation. J Am Chem Soc 2024; 146:18459-18469. [PMID: 38934577 PMCID: PMC11240563 DOI: 10.1021/jacs.4c03911] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Revised: 05/17/2024] [Accepted: 06/11/2024] [Indexed: 06/28/2024]
Abstract
Coevaporation of formamidinium lead iodide (FAPbI3) is a promising route for the fabrication of highly efficient and scalable optoelectronic devices, such as perovskite solar cells. However, it poses experimental challenges in achieving stoichiometric FAPbI3 films with a cubic structure (α-FAPbI3). In this work, we show that undesired hexagonal phases of both PbI2 and FAPbI3 form during thermal evaporation, including the well-known 2H-FAPbI3, which are detrimental for optoelectronic performance. We demonstrate the growth of α-FAPbI3 at room temperature via thermal evaporation by depositing phosphonic acids (PAc) on substrates and subsequently coevaporating PbI2 and formamidinium iodide. We use density-functional theory to develop a theoretical model to understand the relative growth energetics of the α and 2H phases of FAPbI3 for different molecular interactions. Experiments and theory show that the presence of PAc molecules stabilizes the formation of α-FAPbI3 in thin films when excess molecules are available to migrate during growth. This migration of molecules facilitates the continued presence of adsorbed organic precursors at the free surface throughout the evaporation, which lowers the growth energy of the α-FAPbI3 phase. Our theoretical analyses of PAc molecule-molecule interactions show that ligands can form hydrogen bonding to reduce the migration rate of the molecules through the deposited film, limiting the effects on the crystal structure stabilization. Our results also show that the phase stabilization with molecules that migrate is long-lasting and resistant to moist air. These findings enable reliable formation and processing of α-FAPbI3 films via vapor deposition.
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Affiliation(s)
- Andrés-Felipe Castro-Méndez
- School
of Materials Science and Engineering, Georgia
Institute of Technology, North Ave NW, Atlanta, Georgia 30332, United States
| | - Farzaneh Jahanbakhshi
- Department
of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, United
States
| | - Diana K. LaFollette
- School
of Materials Science and Engineering, Georgia
Institute of Technology, North Ave NW, Atlanta, Georgia 30332, United States
| | - Benjamin J. Lawrie
- The
Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- Materials
Science and Technology Division, Oak Ridge
National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Ruipeng Li
- National
Synchrotron Light Source II (NSLS-II), Brookhaven
National Laboratory, Upton, New York 11967, United States
| | - Carlo A. R. Perini
- School
of Materials Science and Engineering, Georgia
Institute of Technology, North Ave NW, Atlanta, Georgia 30332, United States
| | - Andrew M. Rappe
- Department
of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, United
States
| | - Juan-Pablo Correa-Baena
- School
of Materials Science and Engineering, Georgia
Institute of Technology, North Ave NW, Atlanta, Georgia 30332, United States
- School of
Chemistry and Biochemistry, Georgia Institute
of Technology, North Ave NW, Atlanta, Georgia 30332, United States
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2
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Lee MH, Kim DW, Noh YW, Kim HS, Han J, Lee H, Choi KJ, Cho S, Song MH. Controlled Crystal Growth of All-Inorganic CsPbI 2Br via Sequential Vacuum Deposition for Efficient Perovskite Solar Cells. ACS NANO 2024; 18:17764-17773. [PMID: 38935840 DOI: 10.1021/acsnano.4c03079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/29/2024]
Abstract
Vacuum deposition of perovskites is a promising method for scale-up fabrication and uniform film growth. However, improvements in the photovoltaic performance of perovskites are limited by the fabrication of perovskite films, which are not optimized for high device efficiency in the vacuum evaporation process. Herein, we fabricate CsPbI2Br perovskite with high crystallinity and larger grain size by controlling the deposition sequence between PbI2 and CsBr. The nucleation barrier for perovskite formation is significantly lowered by first evaporating CsBr and then PbI2 (CsBr-PbI2), followed by the sequential evaporation of multiple layers. The results show that the reduced Gibbs free energy of CsBr-PbI2, compared with that of PbI2-CsBr, accelerates perovskite formation, resulting in larger grain size and reduced defect density. Furthermore, surface-modified homojunction perovskites are fabricated to efficiently extract charge carriers and enhance the efficiency of perovskite solar cells (PeSCs) by modulating the final PbI2 thickness before thermal annealing. Using these strategies, the best PeSC exhibits a power conversion efficiency of 13.41% for a small area (0.135 cm2), the highest value among sequential thermal deposition inorganic PeSCs, and 11.10% for a large area PeSC (1 cm2). This study presents an effective way to understand the crystal growth of thermally deposited perovskites and improve their performance in optoelectronic devices.
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Affiliation(s)
- Min Hyeong Lee
- Department of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Dae Woo Kim
- Department of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Young Wook Noh
- Department of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Hye Seung Kim
- Department of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Jongmin Han
- Department of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Heunjeong Lee
- Department of semiconductor physics and energy harvest storage research center, University of Ulsan, Ulsan 44610, Republic of Korea
| | - Kyoung Jin Choi
- Department of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Shinuk Cho
- Department of semiconductor physics and energy harvest storage research center, University of Ulsan, Ulsan 44610, Republic of Korea
| | - Myoung Hoon Song
- Department of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
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3
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Wang K, Ecker BR, Ghosh M, Li M, Karasiev VV, Hu SX, Huang J, Gao Y. Light-enhanced oxygen degradation of MAPbBr 3 single crystal. Phys Chem Chem Phys 2024; 26:5027-5037. [PMID: 38258478 DOI: 10.1039/d3cp03493c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Organometal halide perovskites are promising materials for optoelectronic applications, whose commercial realization depends critically on their stability under multiple environmental factors. In this study, a methylammonium lead bromide (MAPbBr3) single crystal was cleaved and exposed to simultaneous oxygen and light illumination under ultrahigh vacuum (UHV). The exposure process was monitored using X-ray photoelectron spectroscopy (XPS) with precise control of the exposure time and oxygen pressure. It was found that the combination of oxygen and light accelerated the degradation of MAPbBr3, which could not be viewed as a simple addition of that by oxygen-only and light-only exposures. The XPS spectra showed significant loss of carbon, bromine, and nitrogen at an oxygen exposure of 1010 Langmuir with light illumination, approximately 17 times of the additive effects of oxygen-only and light-only exposures. It was also found that the photoluminescence (PL) emission was much weakened by oxygen and light co-exposure, while previous reports had shown that PL was substantially enhanced by oxygen-only exposure. Measurements using a scanning electron microscope (SEM) and focused ion beam (FIB) demonstrated that the crystal surface was much roughened by the co-exposure. Density functional theory (DFT) calculations revealed the formation of superoxide and oxygen induced gap state, suggesting the creation of oxygen radicals by light illumination as a possible microscopic driving force for enhanced degradation.
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Affiliation(s)
- Ke Wang
- Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627, USA.
| | - Benjamin R Ecker
- Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627, USA.
| | - Maitrayee Ghosh
- Laboratory for Laser Energetics (LLE), University of Rochester, Rochester, NY 14623, USA
| | - Mingze Li
- Department of Applied Physical Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Valentin V Karasiev
- Laboratory for Laser Energetics (LLE), University of Rochester, Rochester, NY 14623, USA
| | - S X Hu
- Laboratory for Laser Energetics (LLE), University of Rochester, Rochester, NY 14623, USA
| | - Jinsong Huang
- Department of Applied Physical Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Yongli Gao
- Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627, USA.
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Wang K, Ecker B, Li M, Huang J, Gao Y. CuPc Passivation of a MAPbBr 3 Single Crystal Surface. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2023; 127:19599-19606. [PMID: 37817921 PMCID: PMC10561261 DOI: 10.1021/acs.jpcc.3c04209] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 09/10/2023] [Indexed: 10/12/2023]
Abstract
In this study, a facile passivation for methylammonium lead bromide (MAPbBr3) single crystals is reported. Stability against moisture and light remains the most critical demerit of perovskite materials, which is improved by depositing a 40 Å thick hydrophobic copper phthalocyanine (CuPc) layer on top of the cleaved perovskite surface. The water and light exposure processes were monitored with X-ray photoelectron spectroscopy with precise control of the exposure time and pressure. It is found that the CuPc top layer could protect the sample from moisture infiltration at a water exposure of 1013 L, while the nonpassivated sample started to degrade at 108 L. During the light exposure, CuPc also slowed down the light-induced degradation, which is supported by the elemental ratio change of metallic lead and bromine. These results are further confirmed by the morphological comparison via scanning electron microscopy and focused ion beam.
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Affiliation(s)
- Ke Wang
- Department
of Physics and Astronomy, University of
Rochester, Rochester, New York 14627, United States
| | - Benjamin Ecker
- Department
of Physics and Astronomy, University of
Rochester, Rochester, New York 14627, United States
| | - Mingze Li
- Department
of Applied Physical Sciences, University
of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Jinsong Huang
- Department
of Applied Physical Sciences, University
of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Yongli Gao
- Department
of Physics and Astronomy, University of
Rochester, Rochester, New York 14627, United States
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Short-Chain Acid Additives to Control PbI2 Crystallization in Hybrid Perovskite Films. INORGANICS 2022. [DOI: 10.3390/inorganics10080114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The quality and the performance of hybrid perovskite (HP)’s films strongly depend on the complete conversion into MAPbI3 of a spin-coated solution of methylammonium iodide (MAI) and PbI2. Highly crystalline PbI2 on a substrate limits such a conversion and, consequently, the HP’s solar cell performances. We investigate for the first time the use of short-chain organic acids as additives in a non-complexing solvent like γ-butyrolactone (GBL), that can retard retard the crystallization of PbI2. Based on XRD analyses of the spin coated films, the acetic acid is the most effective additive in retarding the PbI2 crystallization, making Pb2+ available for a subsequent reaction with MAI. These results open a new experimental path for fabricating perovskite films by single or sequential step methods involving acid additives.
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Photonic Cavity Effects for Enhanced Efficiency in Layered Perovskite-Based Light-Emitting Diodes. NANOMATERIALS 2021; 11:nano11112947. [PMID: 34835709 PMCID: PMC8622141 DOI: 10.3390/nano11112947] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/03/2021] [Revised: 10/25/2021] [Accepted: 11/01/2021] [Indexed: 12/13/2022]
Abstract
Layered architectures for light-emitting diodes (LEDs) are the standard approach for solution-processable materials such as metal-halide perovskites. Upon designing the composition and thicknesses of the layers forming the LED, the primary focus is typically on the optimization of charge injection and balance. However, this approach only considers the process until electrons and holes recombine to generate photons, while for achieving optimized LED performance, the generated light must also be efficiently outcoupled. Our work focuses on the latter aspect. We assume efficient photon generation and analyze the effects of the geometrical configuration together with the dipole orientation, mimicking the light emission, on the main characteristics defining the LED, such as the Purcell effect and the outcoupling efficiency. We find that in-plane dipoles result in significantly increased outcoupling efficiency. Furthermore, the mismatch in refractive index among the layers and their different thicknesses can be tuned to maximize the Purcell effect and minimize internal losses. The combined optimization of dipole orientation and layer thicknesses can improve the efficiency of the LED up to a factor 10, hence highlighting the importance of considering also the photonic properties of the LED structures if the objective is to maximize the LED performance.
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