Room‐Temperature Formation of Highly Crystalline Multication Perovskites for Efficient, Low‐Cost Solar Cells

Matsui, Taisuke; Seo, Ji‐Youn; Saliba, Michael; Zakeeruddin, Shaik M.; Grätzel, Michaël

doi:10.1002/adma.201606258

Cited by 136 publications

(138 citation statements)

References 28 publications

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“…[32] Given that the coordination capability of DMSO with PbI 2 is much stronger than that of DMF, longer PbI 2 interplanar distances are formed in the DMSO-based system, which is beneficial for the subsequent intercalation of CsI species. [33] Accordingly, we can conclude that DMSO helps to not only improve solubility of the CsPbI 2 Br precursors but also promote RT formation of the cubic CsPbI 2 Br. Afterward, the DMSO molecules are gradually pushed out from PbI 2 interlayers since the intercalated CsI components possess better affinity toward PbI 2 than DMSO molecules.…”

mentioning

confidence: 79%

Morphology Controlling of All‐Inorganic Perovskite at Low Temperature for Efficient Rigid and Flexible Solar Cells

Rao

et al. 2018

Advanced Energy Materials

127

109

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organic components with inorganic cations such as cesium (Cs + ) and rubidium (Rb + ) ions can effectively improve the thermal stability. Recently, all-inorganic cesium lead halide perovskites (CsPbX 3 , X = I, Br, Cl, or mixed halides), which have higher melting points (in excess of 460 °C), [10] have been investigated as thermal stable photoabsorption materials. The CsPbI 2 Br perovskites, which possess a reasonable bandgap of 1.9 eV and considerable phase stability, were emphasized as the main research subject in previous work. [24][25][26][27][28][29][30] To improve the performance of CsPbX 3 -based PSCs, a series of work on composition [18,19] and fabrication [20][21][22][23][24] engineerings have been intensely carried out. Unfortunately, the CsPbX 3 perovskites generally require high-temperature annealing (>250 °C) to form black photovoltaic-active cubic phase, [27][28][29][30] which is energy-consuming and undesirable for multijunction tandem and flexible solar cells. Up to now, it is still challenging to obtain uniform and void-free CsPbX 3 perovskite films via low-temperature solution-processed methods, let alone room temperature (RT) based technologies.In this work, we demonstrate that coordinated solvent dimethylsulphoxide (DMSO) can effectively induce the RT formation of photovoltaic-active CsPbX 3 perovskites, and a simple RT solvent (DMSO) annealing (RTSA) treatment can controllably remove the high boiling point DMSO and result in highly uniform and void-free CsPbX 3 perovskite films, as well as a postannealing treatment at the moderate temperature of 120 °C can further improve the perovskite grain size and crystallinity. These results provide an approach to prepare high quality allinorganic CsPbX 3 perovskite films at RT or a relatively low temperature (<120 °C). Consequently, efficient inverted CsPbI 2 Brbased PSCs were achieved on both glass and flexible substrates.As previously reported, [27] the CsPbI 2 Br perovskite precursor solution in N,N-dimethylformamide (DMF) suffers from a low concentration (≈0.43 m) due to the solubility limitation of bromide. While for the perovskite precursor solution with DMSO as solvent, the stronger coordination interaction between DMSO and the perovskite precursor enables the concentration exceeding 2 m ( Figure S1, Supporting Information), resulting in thicker perovskite films with sufficient light absorption ( Figure S2, Supporting Information). Furthermore, All-inorganic cesium lead halide (CsPbX 3 ) perovskites have emerged as promising photovoltaic materials owing to their superior thermal stability compared to traditional organic-inorganic hybrid counterparts. However, the CsPbX 3 perovskites generally need to be prepared at high-temperature, which restricts their application in multilayer or flexible solar cells. Herein, the formation of CsPbX 3 perovskites at room-temperature (RT) induced by dimethylsulphoxide (DMSO) coordination is reported. It is further found that a RT solvent (DMSO) annealing (RTSA) treatment is valid to control the perovskite cryst...

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confidence: 79%

Morphology Controlling of All‐Inorganic Perovskite at Low Temperature for Efficient Rigid and Flexible Solar Cells

Rao

et al. 2018

Advanced Energy Materials

127

109

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“…The orbitals of the countercations do not significantly contribute to the frontier bands, but influence the perovskite lattice type, lattice constants, and structural stability. Other experimental approaches to short-term stabilization of α-FAPbI 3 (besides rapid thermal quenching) include doping of the material with MA, [22][23][24][25] Cs, [26,27] and both MA and Cs, [28][29][30] but not with organic cations that bond stronger to the inorganic skeleton than FA. The higher the degree of covalent conjugation, the lower is the bandgap, the larger are radii of the excitons, the lower are the exciton binding energies, and, finally, the more efficient is the charge carrier transport in the material.…”

Section: Introductionmentioning

confidence: 99%

Suppressing X‐Migrations and Enhancing the Phase Stability of Cubic FAPbX₃ (X = Br, I)

Oranskaia

Schwingenschlögl

2019

Advanced Energy Materials

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10 4 cm −1 in the visible-to-infrared region, bandgaps of 1.4-2.3 eV depending on A and X, form Wannier excitons of hundreds of Å diameter and tens of meV binding energy, and have high charge carrier diffusion lengths of up to µm. [1][2][3][4] The highest certified perovskite solar cell power conversion efficiency rapidly increased from 3.8% in 2009 to 22.1% in 2016 using hybrid FAPbI 3 doped with 5% MAPbBr 3[5] (and now stands at 24.2% [6] ). MA and FA stand for methylammonium and formamidinium, light polar organic cations formed by the simplest protonated amine NH 2 CH 3 and amidine NH 2 CHNH. Being incorporated into the lead halide crystal lattice, these organic cations participate not only in strong electrostatic and van der Waals interactions with the inorganic skeleton but also in hydrogen H···X bonding between H atoms (organic cation) and X atoms (inorganic skeleton) that is absent in all-inorganic perovskites. Being an electrondeficient π-conjugated system, FA also participates in π-anion π···X bonding with X atoms. [7] Though the organic cations do not directly determine the optoelectronic properties of hybrid perovskites, they do stabilize the inorganic skeleton of "3D" α-FAPbX 3 (cubic phase) and determine its defect properties, especially regarding X-defects. Goal of the present study therefore is to investigate the role of the FA bonding properties in α-FAPbX 3 and to propose promising organic cation doping strategies.The rising star of hybrid perovskite field of solar energy harvesting, α-FAPbI 3 , has a narrower bandgap than well-studied β-MAPbI 3 (tetragonal phase) and, more importantly, is more stable against decomposition and degradation. [8][9][10][11][12][13] Despite many advantages, β-MAPbI 3 has the serious problem that it is intrinsically thermodynamically unstable, decomposing into PbI 2 and MAI (and further into volatile amine and HI), and readily degrades even at moderate operating temperatures when exposed to water and/or oxygen. Lower affinity of α-FAPbI 3 to decomposition and degradation is related to weaker acidity (as a result of aromatic stabilization), larger volume, and stronger bonding with the halides of FA than MA, which manifests in experiment as suppressed hysteresis due to I-migrations. [5,14] The mobile I-defects in β-MAPbI 3 are detrimental not only to the structural stability of the material but also to its charge transport properties when acting as electron-hole recombination centers. [15][16][17] In this respect, it is crucial to understand the influence of FA on the X-migrations in α-FAPbX 3 and to identify ways to manipulate them by introducing stronger bonding organic cations as dopants.Chemical bonding of formamidinium (FA) with the inorganic perovskite skeleton of FAPbX 3 (X = Br, I) is studied with emphasis on the differences to methylammonium: stronger hydrogen bonding, the presence of π-anion bonding, and more sterically hindered motion inside the perovskite inorganic cage. Organic cation dopants fitting in the perovskite cubic cell and being capable of hydroge...

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“…Further improvements in performance could be obtained with further modification of the material composition. For example, FA 0.8 MA 0.1 Cs 0.1 ‐based PSCs exhibited a high PCE of 18.1%, while perovskite films containing a mixture of FAI, PbI 2 , MABr, and PbBr 2 achieved a maximum PCE of 20.8% . The incorporation of Rb cations yielded a further increase in efficiency up to 21.6% .…”

Section: Introductionmentioning

confidence: 99%

Formamidinium‐Based Lead Halide Perovskites: Structure, Properties, and Fabrication Methodologies

Liu

Waqas

et al. 2018

Small Methods

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Formamidinium (FA)‐based perovskites exhibit great potential for photovoltaics since they enable the achievement of power conversion efficiency (PCE) over 22%. The bandgap of FA‐based perovskite is lower than that of the methylammonium‐based one, while the larger ionic radius and dual‐ammonia group of FA ions restrain their movement in close‐packing [PbI6]4− cages, leading to improved stability. Here, the structure and properties of FAPbI3− and FA‐based mixed cation perovkites are discussed. In particular, the issues of polymorphism and stabilization of the desired low‐bandgap crystal phase of FAPbI3 are considered. FAPbI3 exhibits polymorphisms with a photovoltaically unfavorable δ‐phase that is stable at room temperature, and, thus, it is difficult to prepare continuous and compact FAPbI3 with the desired crystal structure, namely, the pure α‐phase. Hence, overcoming the limitations of phase transitions is the critical issue in obtaining high‐quality FA‐based perovskite films, which are a prerequisite for solar cells with high PCEs. Here, the focus is on the fabrication methods of FA‐based perovskite films, namely, additive engineering, intermolecular exchange, interfacial engineering, and chemical vapor deposition. A comprehensive overview of the fabrication methodology for the FA‐based perovskite films is provided to facilitate understanding of the underlying mechanisms.

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Room‐Temperature Formation of Highly Crystalline Multication Perovskites for Efficient, Low‐Cost Solar Cells

Cited by 136 publications

References 28 publications

Morphology Controlling of All‐Inorganic Perovskite at Low Temperature for Efficient Rigid and Flexible Solar Cells

Morphology Controlling of All‐Inorganic Perovskite at Low Temperature for Efficient Rigid and Flexible Solar Cells

Suppressing X‐Migrations and Enhancing the Phase Stability of Cubic FAPbX₃ (X = Br, I)

Formamidinium‐Based Lead Halide Perovskites: Structure, Properties, and Fabrication Methodologies

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Room‐Temperature Formation of Highly Crystalline Multication Perovskites for Efficient, Low‐Cost Solar Cells

Cited by 136 publications

References 28 publications

Morphology Controlling of All‐Inorganic Perovskite at Low Temperature for Efficient Rigid and Flexible Solar Cells

Morphology Controlling of All‐Inorganic Perovskite at Low Temperature for Efficient Rigid and Flexible Solar Cells

Suppressing X‐Migrations and Enhancing the Phase Stability of Cubic FAPbX3 (X = Br, I)

Formamidinium‐Based Lead Halide Perovskites: Structure, Properties, and Fabrication Methodologies

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Suppressing X‐Migrations and Enhancing the Phase Stability of Cubic FAPbX₃ (X = Br, I)