Chemi-Structural Stabilization of Formamidinium Lead Iodide Perovskite by Using Embedded Quantum Dots

Masi, Sofia; Echeverría‐Arrondo, Carlos; Salim, K. M. Muhammed; Ngo, Thi Tuyen; Méndez, Patricio F.; López-Fraguas, Eduardo; Macías-Pinilla, David F.; Planelles, Josep; Climente, Juan I.; Mora‐Seró, Iván

doi:10.1021/acsenergylett.9b02450

Cited by 100 publications

(175 citation statements)

References 60 publications

(119 reference statements)

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“…The latter effect is in fact the reason why at higher concentration of PbS NPLs, the perovskite is more stable than the perovskite without PbS NPLs, even if the grains were no more prevalently bigger and well ordered. [32] The interaction between the perovskite and the NPLs is quantified with Williamson-Hall analysis. [55] Upon increasing the NPL concentration, the peaks corresponding to the (100) and (200) planes shift (Figure 3c) and the strain is up to 26% higher than in the bare perovskite, see Figure 3d.…”

Section: Resultsmentioning

confidence: 99%

“…To shed light on the effect that the PbS NPLs have on the crystallinity, XRD analysis was performed. The XRD spectra show the characteristics peaks of the FA 0.9 Cs 0.1 PbI 3 α‐phase (ICSD 250736) at 14.03° (100), 20.08° (110), 24.32° (111), 28.20° (200), 31.62° (120), and 40.30° (220), [ 32,52 ] see Figure 3 a. The highest ratio between the (100) and (110) peak intensities is observed for the 1 mg mL −1 and especially for the 0.5 mg mL −1 samples, see Table S2, Supporting Information.…”

Section: Resultsmentioning

confidence: 99%

“…[ 32 ] Beyond that, inorganic PbS quantum dots (QDs) with similar lattice parameter are incorporated into the perovskite matrix for a bulk‐epitaxial growth of the perovskite. The key role of PbS QDs lies at the atomic level, either to promote perovskite crystallization [ 33–35 ] or to improve the stability, according to a chemi‐structural mechanism, [ 32 ] with the additional benefit of preserving the bandgap of FAPbI 3 . In particular, the structural matching between the FAPbI 3 α‐phase and the (100) PbS facets [ 36 ] results in a stabilization of the α‐phase with respect to the δ‐phase.…”

Section: Introductionmentioning

confidence: 99%

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Preferred Growth Direction by PbS Nanoplatelets Preserves Perovskite Infrared Light Harvesting for Stable, Reproducible, and Efficient Solar Cells

Sánchez-Godoy

Erazo

Gualdrón‐Reyes

et al. 2020

Advanced Energy Materials

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Due to its impressive properties such as a high absorption coefficient, long diffusion length and low exciton dissociation energy, [2] the perovskite has been exploited in several applications, among them light amplifiers and lasers, [3-,5] light emitting diodes (LEDs), [6-8] and photovoltaic devices. [9,10] The halide perovskite structure, ABX 3 [11] allows multiple atom combinations, making it very versatile. In addition, it can be synthesized at a low temperature permitting a relatively easy synthesis by a broad range of methods. The monovalent cation A (formamidinium [FA], [12] methylammonium [MA], [13] or cesium [14]) is located in the cage of BX 6 4− octahedra, where B is the metal (commonly, lead or tin) and X a halide or combination of them. The most studied hybrid-perovskite materials are MAPbI 3 and FAPbI 3. Both compounds result in a perovskite structure, despite the difference in the tolerance factor (0.95 and 1.03, respectively, and the same octahedral factor. [15,16] MAPbI 3 is intrinsically phase stable at ambient Formamidinium-based perovskite solar cells (PSCs) present the maximum theoretical efficiency of the lead perovskite family. However, formamidinium perovskite exhibits significant degradation in air. The surface chemistry of PbS has been used to improve the formamidinium black phase stability. Here, the use of PbS nanoplatelets with (100) preferential crystal orientation is reported, to potentiate the repercussion on the crystal growth of perovskite grains and to improve the stability of the material and consequently of the solar cells. As a result, a vertical growth of perovskite grains, a stable current density of 23 mA cm −2 , and a stable incident photon to current efficiency in the infrared region of the spectrum for 4 months is obtained, one of the best stability achievements for planar PSCs. Moreover, a better reproducibility than the control device, by optimizing the PbS concentration in the perovskite matrix, is achieved. These outcomes validate the synergistic use of PbS nanoplatelets to improve formamidinium long-term stability and performance reproducibility, and pave the way for using metastable perovskite active phases preserving their light harvesting capability.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Preferred Growth Direction by PbS Nanoplatelets Preserves Perovskite Infrared Light Harvesting for Stable, Reproducible, and Efficient Solar Cells

Sánchez-Godoy

Erazo

Gualdrón‐Reyes

et al. 2020

Advanced Energy Materials

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“…As mentioned above, the biggest difference between solution-processing versus thermal evaporation of perovskite materials in terms of film composition is the possibility to utilize additives via solution-processing. A broad range of additives has been investigated thus far including materials such as salts, [48] organic molecules and polymers, [49,50] inorganic nanoparticles, [51] and metal ions. [52] These additives have been shown to passivate defects, eliminate hysteresis, improve the layer microstructure, and stabilize the photovoltaically active perovskite crystal phase, leading to superior performance over reference devices that do not include additives.…”

Section: Controlling the Perovskite Compositionmentioning

confidence: 99%

The Future of Perovskite Photovoltaics—Thermal Evaporation or Solution Processing?

Vaynzof

2020

Advanced Energy Materials

161

148

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single solution, which is deposited onto the substrate, following by a thermal annealing step. [6,7] While this approach is very simple and is still relatively common for certain perovskite compositions, [8,9] the perovskite precursors maybe undergo various chemical reactions in solution, which will influence both the resulting film and the performance of photovoltaic devices. [10] An alternative approach, especially popular in the early days of perovskite research, is the two-step approach, in which one of the precursors is deposited first, followed by the deposition of a second precursor and thermal annealing. [11] Most commonly, the first precursor (e.g., lead iodide, PbI 2) is deposited by spin-coating, while the second one (e.g., methylammonium iodide, MAI) can be deposited by dipping the sample into a solution, [12] or by spin-coating on top of the first layer. [13] For a time, devices fabricated using the two-step method showed higher performance than those made using the one-step, [14] but the situation drastically changed upon the introduction of the solvent engineering approach, [15] which remains the most commonly used to date. This method is a modification of the one-step approach, with all perovskite precursors deposited in a single step, during which an antisolvent is applied triggering the crystallization of the perovskite film. [16] Similarly, several variations of deposition of perovskite layers by thermal evaporation have also been demonstrated. These include the single-source evaporation, sequential evaporation and multiple source coevaporation (Figure 1). Single-source evaporation is possible either via combining the perovskite precursors into a single crucible [17] or by first preparing (e.g., via solution-processing) perovskite crystals that are ground into a powder for evaporation. [18] Sequential evaporation follows a similar approach to that of the two-step solution-processed deposition, with each precursor evaporated separately, following by a thermal or vapor annealing. [19] The most common approach, however, is based on the multisource evaporation, in which each precursor is loaded into a separate crucible and is coevaporated along with all other precursors to form the perovskite layer. Importantly, unlike solution-processed perovskite films, it is possible to form crystalline perovskite layers by thermal evaporation without annealing; [20] however, many studies still rely on annealing for improving the evaporated films' properties. [21,22] It is noteworthy that many additional methods for the deposition of perovskite films exist such as inkjet printing, [23] spray coating, [24] chemical vapor deposition, [25] flash evaporation, [26] and many others; [27] however, these methods are less common in literature and generally show lower performance than those fabricated by the methods outlined above. The last decade has seen remarkable advancements in the field of perovskite materials and photovoltaic technologies. One of their most extraordinary characteristics is the high quality of layer...

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“…Photoactive α-perovskite phases within CsxMAyFA1-x-yPbI3 exhibit a bandgap of ~1.5 eV, whereas their main degradation products under hot and humid conditions, PbI2 (2.27 eV), 23 δ-CsPbI3 (2.82 eV) 24 or δ-FAPbI3 (2.43 eV) 25 show deteriorated photophysical properties (Fig. S2).…”

Section: Figurementioning

confidence: 99%

A Physical Data Fusion Approach to Optimize Compositional Stability of Halide Perovskites

Sun

Tiihonen²,

Oviedo³

et al. 2020

Preprint

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Compositional search within multinary perovskites employing brute force synthesis are prohibitively expensive in large chemical spaces. To identify the most stable multi-cation lead iodide perovskites containing Cs, formamidinium (FA) and methylammonium (MA), we fuse results from density functional theory (DFT) calculations and in situ thin-film degradation test within an end-to-end machine learning (ML) algorithm to inform the compositional optimization of CsxMAyFA1-x-yPbI3. We integrate phase thermodynamics modelling as a probabilistic constraint in a Bayesian optimization (BO) loop, which effectively guides the experimental search while considering both structural and environmental stability. After three optimization rounds and only sampling 1.8% of the compositional space, we identify thin-film compositions centred at Cs0.17MA0.03FA0.80PbI3 that achieve a 3x delay in macroscopic degradation onset under elevated temperature, humidity, and light compared with the more complex state-of-the-art Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3. We find up to 8% of MA can be incorporated into the perovskite structure before stability is significantly compromised. Cs is beneficial at low concentrations, however, beyond 17% is found to contribute to reduced stability. Synchrotron-based grazing-incidence wide-angle X-ray scattering (GIWAXS) further validates that the interplay of chemical decomposition and phase separation governs the non-linear instability landscape of this compositional space. We reveal the detrimental role of the ẟ-CsPbI3 minority phase in accelerating degradation and it can be kinetically suppressed by co-optimising Cs and MA content, providing insights into simplifying perovskite compositions for further environmental stability enhancement. Our approach realizes the effectiveness of ML-enabled data fusion in achieving a holistic, efficient, and physics-informed experimentation for multinary systems, potentially generalisable to materials search in the vast structural and alloyed spaces beyond halide perovskites.

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Chemi-Structural Stabilization of Formamidinium Lead Iodide Perovskite by Using Embedded Quantum Dots

Cited by 100 publications

References 60 publications

Preferred Growth Direction by PbS Nanoplatelets Preserves Perovskite Infrared Light Harvesting for Stable, Reproducible, and Efficient Solar Cells

Preferred Growth Direction by PbS Nanoplatelets Preserves Perovskite Infrared Light Harvesting for Stable, Reproducible, and Efficient Solar Cells

The Future of Perovskite Photovoltaics—Thermal Evaporation or Solution Processing?

A Physical Data Fusion Approach to Optimize Compositional Stability of Halide Perovskites

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